Chemical switching of taxo-diterpenoids between low solubility active forms and high solubility inactive forms

ABSTRACT

Cyclic chemical switching method is employed for solubilizing and desolubilizing taxo-diterpenoids with respect to aqueous solvents. 2-Halogenated onium salts of aza-arenes are employed to derivatize taxo-diterpenoids so as to alter their solubility in aqueous solvents. The onium salt of aza-arene includes a delocalized charge which imparts polarity and aqueous solubility to taxo-diterpenoid derivatives. Solubilization is achieved in a one step derivatization with the onium salt of 2-halogenated aza-arenes. Desolubilization is achieved by contacting onium salts of taxo-diterpenoid-C n ,2-O-aza-arenes with serum protein to displace the 2-O-aza-arene and form a soluble protein:taxo-diterpenoid intermediate. This protein:taxo-diterpenoid intermediate then dissociates over time to provide a bioactive taxo-diterpenoid. These same onium salts of taxo-diterpenoid-C n ,2-O-aza-arenes are employed as water soluble prodrugs. The toxicity of the activated form is comparable or greater than underivatized taxol. The invention is applicable to taxol and taxol memetics having hydroxyls that are reactive with onium salts of 2-halogenated-aza-arenes.

DESCRIPTION

This is a 371 of PCT/US95/00481, filed on Jan. 10, 1995 which is acontinuation of U.S. Pat. No. 08/180,135 filed Jan. 11, 1994, nowabandoned.

This invention was made with government support under Contract No. CA46446 by the National Institutes of Health. The government has certainrights in the invention.

TECHNICAL FIELD

The invention relates to taxol prodrugs. More particularly, theinvention relates to a method employing derivatization with onium saltsof 2-halogenated aza-arenes for chemically switching between lowsolubility active forms and high solubility inactive forms of taxol andtaxol memetics.

BACKGROUND

Taxol, an antineoplastic agent originally isolated from Taxusbrevifolia, is approved for usage in the treatment of ovarian cancer andis expected to see usage in breast, lung, and skin cancers as well.However, since Taxol possesses an extremely low water solubility, i.e.,less than 1.5×10⁻⁶ molar, it has been necessary to formulate Taxol in amixture of Cremaphor™, a polyoxyethylated castor oil, and ethanol inorder to achieve a therapeutic concentration. This formulation caninduce a variety of significant side effects including hypersensitivityreactions.

While premedication and slow administration of the drug can circumventthese problems in the clinic, the entire protocol is quite cumbersomeand requires extensive close monitoring of patients. Although taxol'sdramatic efficacy has driven clinical usage forward despite theseproblems, a water soluble form of taxol could completely obviate theneed for this troublesome protocol.

One approach to bypassing these formulation difficulties, previouslyattempted by several groups including our own, is the introduction ofsolubilizing functionality that normal metabolic pathways could removein vivo. Compounds of this type, termed prodrugs, consist, in the caseof taxol, primarily of ester derivatives at the 2′ and 7 positions.Currently none of these protaxols have given success in the clinic. Ineach case, the prodrug is rapidly cleared from circulation by thekidneys.

Taxol is only one of a class of taxo-diterpenoids having bioactivity.Another preferred taxo-diterpenoid having clinically significantactivity is Taxotere™. Unfortunately, all known bioactivetaxo-diterpenoids have a low aqueous solubility.

What is needed is a method for chemically switching taxol and othertaxo-diterpenoids between a high solubility and low solubility form in amanner which regulates its rate of clearance from circulation so thatthe prodrug is retained for a clinically significant period afteradministration.

Taxol itself is known to serve as a chemical switch with respect totubulin. Binding of taxol to tubulin prevents its polymerization and theformation of microtubules. While unpolymerized tubulin is soluble inaqueous media, polymerization of tubulin leads to the formation ofinsoluble microtubules. Accordingly, the addition or removal of taxoldrives the depolymerization or polymerization of tubulin and, in thismanner, serves as a chemical switch for regulating the solubility oftubulin.

SUMMARY

The invention is a cyclic method employing chemical switching forsolubilizing and desolubilizing taxo-diterpenoids with respect toaqueous solvents. The invention employs 2-halogenated onium salts ofaza-arenes to derivatize taxo-diterpenoids so as to alter theirsolubility in aqueous solvents. The onium salt of aza-arene includes adelocalized charge which imparts polarity and aqueous solubility totaxo-diterpenoid derivatives. Solubilization includes a one stepderivatization with the onium salt of 2-halogenated aza-arenes.Contacting onium salts of taxo-diterpenoid-C^(n),2-O-aza-arenes with theserum protein, causes the displacement of 2-O-aza-arene and theformation of a soluble protein:taxo-diterpenoid intermediate. Thisprotein:taxo-diterpenoid intermediate then dissociates over time toprovide a bioactive taxo-diterpenoid. Preferred taxo-diterpenoidsinclude taxol, C-2 substituted analogs of taxol, and Taxotere™.Taxo-diterpenoid-C^(n),2-O-aza-arene may be produced in a one stepsynthesis by reacting onium salts of 2-halogenated aza-arenes withreactive hydroxyls on the taxo-diterpenoid. Reactive hydroxyls on taxoland Taxotere™ are located at C²′ and C⁷. A preferred onium salt of2-halogenated aza-arene is 2-fluoro-1-methylpyridinium tosylate. Otheremployable onium salts of 2-halogenated aza-arenes are disclosed by T.Mukaiyama, Angewandte Chemie 1979,18(18), 707-808, incorporated hereinby reference.

More particularly, a first embodiment of the invention is directed acyclic method employing chemical switching for solubilizing anddesolubilizing taxo-diterpenoids with respect to aqueous solvents.Underivatized forms of the taxo-diterpenoid have low aqueous solubilityand include a reactive C^(n)-hydroxyl, i.e., a reactive hydroxyl at theC^(n) position. Preferred reactive C^(n) hydroxyls for taxol andTaxotere™ are located at positions C^(2′) and C⁷. The method includestwo steps. In the first step, the underivatized form of thetaxo-diterpenoid is converted from low solubility to high solubility byderivatizing the reactive C^(n)-hydroxyl with the onium salt of the2-halogenated aza-arene to form the onium salt of ataxo-diterpenoid-C^(n),2-O-aza-arene derivative having high solubility.In the second step, the onium salt of thetaxo-diterpenoid-C^(n),2-O-aza-arene derivative is converted from highsolubility to low solubility by contacting thetaxo-diterpenoid-C^(n),2-O-aza-arene derivative with serum protein fordisplacing the 2-O-aza-arene and forming a protein:taxo-diterpenoidintermediate. The protein:taxo-diterpenoid intermediate has a highsolubility but then dissociates over time to produce the underviatizedform of the taxo-diterpenoid employed in the first step, i.e., thetaxo-diterpenoid is released from the protein:taxo-diterpenoidintermediate. The precise nature of the bonding between serum proteinand the taxo-diterpenoid within the protein:taxo-diterpenoidintermediate has not been characterized, but can be stable over a periodranging from minutes to hours. A first alternative embodiment of theinvention are directed to the derivatization of taxo-diterpenoids withonium salts of 2-halogenated aza-arenes. A second alternative embodimentis directed to conversion of onium salts oftaxo-diterpenoid-C^(n),2-O-aza-arene derivatives toprotein:taxo-diterpenoid intermediates using serum protein. In thissecond alternative embodiment, the taxo-diterpenoid-C^(n),2-O-aza-arenederivative is contacted with serum protein for displacing the2-O-aza-arene and forming the protein:taxo-diterpenoid intermediate.

In a preferred embodiment, the taxo-diterpenoid-2-O-aza-arenes arerepresented by the following formula:

wherein R^(x) is Ph or tBuO; R¹⁰ is OAc or OH; RY is a C-2 substituentdefined below; and R^(2′) and R⁷ are each selected from the groupconsisting of OH and an onium salt of a 2-O-aza-arene, with the provisothat at least one of R^(2′) and R⁷ is the onium salt of the2-O-aza-arene. The onium salt of the 2-O-aza-arene can be represented byeither of the following formulas for onium salt I or onium salt II:

wherein Z¹ and Z² are each either C or N; Z³ is S or O; R¹ is selectedfrom the group consisting of C₁-C₆ alkyl, allyl, arenxyl, propargyl, andfused aryl; R² and R⁶ are each selected from the group consisting of H,C₁-C₆ alkyl, allyl, arenxyl, propargyl, and fused aryl; if Z¹ is C, thenR³ is selected from the group consisting of H, C₁-C₆ alkyl, allyl,arenxyl, propargyl, C₁-C₆ O-alkyl, OH, halogen, and fused aryl; if Z¹ isN, then R³ is absent; R⁴ and R⁸ are each selected from the groupconsisting of H, C₁-C₆ alkyl, allyl, arenxyl, propargyl, C₁-C₆ O-alkyl,OH, halogen, and fused aryl; and if Z² is C, then R⁵ is selected fromthe group consisting of H, C₁-C₆ alkyl, allyl, arenxyl, propargyl, C₁-C₆O-alkyl, OH, halogen, and fused aryl; if Z² is N, then R⁵ is absent; andS- is a counter ion.

R^(y) is a C-2 substituent. Preferred C-2 substituents are representedby the following structures:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates the kinetics of taxol release from taxol-2′-MPT (2)in various aqueous solutions at 25° C. (horizontal line). Althoughstable in water and aqueous buffer solutions, methylene chlorideextraction of plasma treated with compound 2 showed complete conversionof 2 into taxol (1) within 10 minutes (curve, 20% of total recovered).

FIG. 2A illustrates a transmission electron micrograph (TEM) ofself-assembled helical fibrous nanostructures of taxol-2′-MPT, i.e.,compound 2 in buffered solutions (2,1 mM in 100 mM PBS) above thecritical aggregation concentration (CAC) of this compound using anegative phosphotungstate stain and a magnification of ×25000. The insetshows a portion of one of the fibrils further magnified to illustratethe helical nature of the structure.

FIG. 2B illustrates a transmission electron micrograph (TEM) ofself-assembled spherical nanostructures of taxol-2′-MPT (compound 2) inunbuffered solutions (2,1 mM in H₂O) above the critical aggregationconcentration (CAC) of this compound using a negative uranyl acetatestain and a magnification of ×45000.

FIG. 3 illustrates a tubulin polymerization-depolymerizationmeasurements with negative control (triangles), positive taxol control(diamonds), and taxol-2′-MPT, i.e., compound 2 (dots). Calcium chloridepromoted depolymerization is suppressed by taxol but not bytaxol-2′-MPT.

FIG. 4 illustrates the relative cytotoxicities of taxol-2′-MPT (compound2) and taxol against a variety of cell lines.

FIG. 5 illustrates the efficacy of taxol-2′-MPT in lung tumor xenograftnude mouse model: 5% dextrose (triangles), taxol (diamonds), andtaxol-2′-MPT (dots).

DETAILED DESCRIPTION

The synthesis, physical properties, and pharmaceutical profiles of watersoluble onium salts of taxo-diterpenoid-C^(n),2-O-aza-arenes aredescribed.

Synthesis of Taxol-2′-MPT

Taxol-2′-MPT (methylpyridinium tosylate), compound 2, was synthesizedaccording to the method of T. Mukaiyama, Angewandte Chemie 1979, 18(18),707-808, incorporated herein by reference. Taxol (10 mg, 0.012 mM), fromNaPro Biochemicals, Boulder Col., USA, was dried by azeotropicdistillation with toluene (2×1.0 mL) and then dissolved in methylenechloride (0.4 mL) and treated sequentially under an atmosphere of dryargon, with freshly distilled triethylamine (5 microL, 0.04 mM, 3equivalents) and 2-fluoro-1- methylpyridinium tosylate (5 mg, 0.018 mM,1.5 equivalents) Aldrich Chemicals, and allowed to stir at ambienttemperature for 30 minutes. The clear colorless solution rapidly turnedto a clear pale yellow. The course of the reaction was monitored throughthin layer chromatography (TLC) (E. Merck RP-18 silica, 65tetrahydrofuran:35 water, UV/phosphomolybdic acid) and after thirtyminutes of stirring at ambient temperature, judged complete as no taxolremained and only one compound was apparent by TLC (Rf 0.8).Purification via reverse phase high pressure liquid chromatography(HPLC) (C₁₈ column, 1 mM NH₄O Ac pH 6.5 buffer/methanol gradient, 1.5mL/min. UV) to give, after removal of solvent in vaccuo, puretaxol-2′-MPT (2) (12 mg, 93% yield) as a white amorphous solid. Allspectroscopic data (¹H NMR and HRMS) were in accord with the structureassigned to 2. ¹H NMR (CDCl₃, 125 MHz): 1.055 (s, 3 H, C17-H), 1.083 (s,3 H, C19-H), 1.724 (s, 3 H, C19-H), 1.858 (m, 1 H, C6- H), 1.913 (s, 3H, CH₃-Ph), 2.193 (s, 3 H, C10-OC(O)CH₃), 2.514 (m, 1 H, C6-aH), 3.663(d, 1 H, J=7.0 Hz, C3-H), 4.110 (d, 1 H, J=8.5, C20- H, A of AB), 4.133(s, 3 H, N-CH₃), 4.230 (d, 1 H, J=8.5, C20-aH, B of AB), 4.315 (dd, 1 H,J=8.7, 10.7, C7-H), 4.901 (dd, 1 H, J=1.0, 7.7, C5-H), 5.501 (d, 1 H,C2-H, J=7.0), 5.702 (bt, 1 H, C2′-H, J=8.0), 5.951 (dd, 1 H, C13-H,J=1.0, 8.0), 6.120 (bd, 1 H, C3′-H, J=10.0), 6.181 (s, 1 H, C10-H) 7.702(t, 1 H, N-H, J=7.5), 7.33-7.45 (m, 8 H, Ar-H), 7.56-7.62 (m, 4 H,Ar-H), 7.56-7.62 (m, 4 H, Ar-H), 7.68-7.75 (m, 4 H, Ar-H), 8.00-8.05 (m,1 H Ar-H), 8.23-8.28 (m, 1 H, Pyr-H), 8.41 (m, 1 H, Pyr-H). IR (neat,KCl plate) cm⁻¹: 3640-3120 (bm), 3030-2870 (bm), 2320 (m), 1720 (s),1630 (m), 1560 (m), 1500 (m), 1360 (s), 1160 (m), 1070 (m), 700 (m).UV/Vis (CHCl₃) nm: 254, 280. FAB HRMS: calc for C₅₃H₅₇O₁₄N₂: 945.3810;found: 945.3810

The molecular structures of taxol, compound 1, and of taxol-2′-MPT,compound 2, are illustated in Scheme 1A. The synthesis of taxol-2′-MPTis illustrated in Scheme 1B.

Synthesis of Taxol-7-MPT:

The synthesis of taxol-7-MPT differed only slightly from the synthesisof Taxol-2′-MPT. Taxol (10 mg, 0.012 mM), from NaPro Biochemicals,Boulder Col., USA, was dissolved in methylene chloride (2.0 mL) andtreated sequentially with triethylamine (67 microL, 0.48 mM, 40equivalents) and 2-fluoro-1- methylpyridinium tosylate (34 mg, 0.12 mM,10 equivalents) Aldrich Chemicals, and allowed to stir at ambienttemperature for 5 minutes. Purification via reverse phase high pressureliquid chromatography (HPLC) gave pure taxol-2′-MPT (2) (12 mg, 93%yield) as a white amorphous solid. The Rf of taxol-7-MPT is about 0.3minutes less than the Rf of taxol-2′-MPT. The yield was 11 mg or 85%.Spectroscopic data (¹H NMR and HRMS) were as expected.

Synthesis of Taxol-bis-2′,7-MPT

The synthesis of taxol-bis-2′,7-MPT differed from the synthesis ofTaxol-7-MPT only with respect to reaction time. Taxol (10 mg, 0.012 mM),from NaPro Biochemicals, Boulder Col., USA, was dissolved in methylenechloride (2.0 mL) and treated sequentially with triethylamine (67microL, 0.48 mM, 40 equivalents) and 2-fluoro-1- methylpyridiniumtosylate (34 mg, 0.12 mM, 10 equivalents) Aldrich Chemicals, and allowedto stir at ambient temperature for 18 hours. Purification via reversephase high pressure liquid chromatography (HPLC) gave pure taxol-2′-MPT(2) (12 mg, 93% yield) as a white amorphous solid. The Rf oftaxol-bis-2′,7-MPT is about 0.3 minutes less than the Rf oftaxol-2′-MPT. The yield was 13 mg or 85%. Spectroscopic data (¹H NMR andHRMS) were as expected.

Alternative synthetic schemes based upon the method of T. Mukaiyama(Angewandte Chemie 1979, 18(18), 707-808) using a variety of onium saltsof 2-halogenated aza-arenes for derivatizing either the 2′ or the 7positions of taxol are illustrated in the following scheme:

Stability measurements and Kinetics of Taxol release

Due to a difference in retention time using our standard HPLC conditions(see FIG. 1) and differing ultraviolet absorption maxima (1₂₈₀/1₂₅₄=1.6for 2 and 0.3 for 1), the stability of 2 was easily assayed by HPLC(FIG. 1). In all of the ensuing studies, the only degradation productsdetected were taxol and the pyridinone that results from hydrolysis ofpyridinium salts (FIG. 1c.). Taxol-2′-MPT appears completely stable inthe solid state in a temperature range of −80° C. to 25° C. regardlessof the presence of an inert atmosphere. In water, 5% dextrose, and 1.5%saline 2 is stable for several days but begins to exhibit slowdegradation after 4 days. In phosphate buffered saline (PBS) or ammoniumacetate—phosphate buffer systems of pH 6.0 to 7.3, 2 is stable at 25° C.for over 21 days. Taxol-2′-MPT (2) is, however, unstable in 5% HCl (pH1.1) and brine. Most significantly, 2 breaks down rapidly when incubatedat 37° C. with human plasma. This result suggests the presence offactors within plasma that initiate the degradation of 2 to taxol. Sincetaxol has been shown to bind to albumin to the extent of ca. 85% insera, it is suspected that basic lysine residues on this protein mayinitiate breakdown.

The kinetics of taxol release from taxol-2′-MPT (2) in various aqueoussolutions at 25° C. is shown in FIG. 1. In sterile water, pH 6.2phosphate buffered saline, or 5% dextrose, no taxol release is observedover a period of 11 minutes, as shown by the horizontal line. Althoughstable in water and aqueous buffer solutions, methylene chlorideextraction of plasma treated with compound 2 showed complete conversionof 2 into taxol (1) within 10 minutes, as shown by the curved line.Under these conditions 20% of total is recovered. More particularly,Taxol-2′-MPT (2) was dissolved in the aqueous system with the aid ofsonication for five minutes. Aliquots were then removed at the timesshown and partitioned into methylene chloride to quench the reaction.Samples were then analyzed using a Waters Maxima HPLC instrumentequipped with an autoinjector (3.9×300 mm C₁₈ column equipped with aprecolumn. The flow rate was 1.5 mL/minute. The eluent gradient A-Bextended over 30 minutes. “A” was 80% 80 mM ammonium acetate, pH 6.0.“B” was 100% methanol. An ultraviolet diode array detector was employed.The ratio of compound 2 (Rf 16.2 min.) to taxol (compound 1, Rf 16.8min.) remaining was determined from the relative areas of the peaksafter normalization with previously determined calibration curves.

Solubility Measurements

The solubility and partition coefficient data for 2 and taxol weredetermined using an HPLC method.

Taxol 2′-MPT-taxol Solubility in Water <1.5 × 10⁻⁶ 1.7 × 10⁻³ PartitionCoefficient >10000 50 [octanol/[water]

Solubility was found by forming a solution in water with the aid ofsonication for five minutes, centrifugation of the samples, andinjection of the supernatant. The values reported were normalized usingcalibration curves constructed for both compounds by preparing knownconcentrations in the range 1×10⁻⁶ to 1×10⁻³ M in methylene chloride andsubjecting to HPLC analysis under the same conditions. One should notethat the solubility of taxol is at the detection limit of the instrumentand thus represents an upper limit. The solubility of 2 was found at aconcentration at which the solution was clear (see below) and thusrepresents a lower limit. Compound 2 exhibited similar solubilities forvarious buffer systems in the pH range 6.2 to 7.4. Partitioncoefficients were determined by dissolving the compound in the organicphase, shaking the resulting solution with water for ten minutes, andanalyzing each phase by HPLC as above. No degradation of 2 was notedduring these studies. These data clearly show that 2 is significantlymore soluble in water than the parent taxol. The solubility demonstratedin a range of aqueous systems is higher than the clinically relevantdosages (3 to 30 mM).

Self-Assembling Structures

While the water solutions of 2 were optically clear at allconcentrations examined, buffered solutions of concentrations greaterthan 1×10⁻³ M exhibited a haze to the naked eye and diffuse scatteringof monochromatic light. Ultraviolet spectroscopic absorptionmeasurements at 340 nm (FIG. 3) showed an exponential increase inoptical density (OD) above a critical concentration of 4×10⁻⁴ M, aresult characteristic of macromolecular structure in solution.Transmission electron microscopy (TEM) confirmed the presence ofsupramolecular structures in these solutions. Uniform aggregates offibrillar structure (FIG. 2a) with helical conformations were observed.These structures exhibited varying (up to 800 Å) lengths but consistentdiameter of ca. 80 Å with a helical twist of about 7. Additionally,freshly sonicated solutions of 2 showed the presence of sphericalstructures (FIG. 2b) with diameters of about 50 Å. It is likely that thelong term stability of these solutions is due, at least in part, tostabilization provided by this structured environment.

Microtubule polymerization-depolymerization measurements

Microtubule polymerization-depolymerization measurements (FIG. 3) withtaxol-2′-MPT (2) were very similar to GTP-saline controls anddrastically different from taxol. Compound 2 does not appear to bind totubulin in the manner of taxol. In the buffered aqueous environment ofthis assay, 2 is not converted to taxol and thus does not affect thetubulin-microtubule equilibria. Taxol, recovered from human plasmatreated with 2, exhibited the expected microtubule stabilization,indicating that 2 does act as a prodrug for taxol.

Tubulin polymerization-depolymerization measurements are illustrate inFIG. 3. Negative controls are shown with triangles; positive taxolcontrols are shown with diamonds; and taxol-2′-MPT, i.e., compound 2 isshown with dots. The measurements indicate that calcium chloridepromoted depolymerization is suppressed by taxol but not bytaxol-2′-MPT.

More particularly, measurement were performed in 96 well plates at 37°C. following the protocol of R. Merlock and W. Wrasidlo (AnalyticalBiochemistry 1993, in press). Calcium chloride addition is indicated bythe arrow. In each case, 1.0 mM GTP was used to promote the initialpolymerization of tubulin. Negative control employed tubulin (1.0 mg/mL)alone, CaCl₂ (0,25 mM) added after 20 minutes. Positive taxol controlemployed tubulin (1.0 mg/mL) with taxol (10⁻⁶ M) and CaCl₂ (0.25 mM)added after 20 minutes. The experimental taxol-2′-MPT employed tubulin(1.0 mg/mL) with taxol-2′-MPT (10⁻⁶) and CaCl₂ (0.25 mM) added after 20minutes. Turbidity was measured as optical density at 340 nm using amicroplate reader (Molecular Devices Thermomax).

Toxicity Measurements

Compound 2 was tested for its cytotoxicity against a cell line panelincluding leukemia, ovarian, lung, and breast carcinoma cells (FIG. 4).The differential cytotoxicity profiles for 2 and taxol were similar,although some differences were noted. Both compounds exhibited IC₅₀values ranging from 10⁻⁵ to 10⁻¹² M with means close to one nanomolar.Normal cells had cytotoxicity levels three to four orders of magnitudebelow mean values. Extremely high cytotoxicity levels were recorded forhuman leukemia, metastatic melanoma and cervical carcinoma. As expectedfor a prodrug of taxol in the cellular environment, 2 shows the sameremarkable tumor cell selectivity and cell line specificity as taxol.

The relative cytotoxicities of taxol-2′-MPT (compound 2) and taxolagainst a variety of cell lines are illustrated in FIG. 4. Moreparticularly, cells were plated on 96 well plates with the followingcontrols: no cells and toxic control (1×10⁻³ M SDS). The drug was addedto the first set of wells and diluted via standard dilution method fromthe stock. Plates were incubated at 37° C., 5% CO₂ in sterile air in anhumidified incubator for 72 hours. An aliquot of 50 L of a solution of2,3-bis(methoxy-4-nitro-5-sulfophenyl)-5-[(phenylamino)carbonyl]-1H-tetrazoliumhydroxide (XTT), 1 mg mL⁻¹, in phosphate buffered saline (PBS, 100 mM)was added to the wells. In the presence of viable cells, this colorlessclear media is enzymatically altered to give a pink coloration. Theplates were read at 450 nm using a plate reader. Percentage cytotoxicitywas calculated using the formula: %C=1—(OD toxin)(OD growth control)⁻¹(100).

Efficacy of taxol-2′-MPT in lung tumor xenograft

The encouraging in vitro data obtained with taxol-2′-MPT (2) prompted usto study its in vivo action using nude mice inflicted with human lungcarcinoma xenografts (FIG. 1). The samples of 2 used for this study wereformulated in sterile PBS without Cremaphor™, indicating the suitabilityof this compound for simple bolus administration. Preliminary data showsthat the control of tumor growth exhibited by 2 is at least comparableto that of taxol and significantly (0.001 p-value, multiple linearregression model) different from controls. These results provide areasonable indication that 2 is converted rapidly to taxol in vivo andshould thus exhibit pharmacology similar to taxol. Indeed, in metabolicstudy using tritiated 2, only 5% of the compound was excreted throughthe kidneys, a result that is completely in accord with the behavior oftaxol.

The efficacy of taxol-2′-MPT in lung tumor xenograft nude mouse model isillustrated in FIG. 5. The tumor model was generated from an ATCC A549non-small cell lung adenocarcinoma cell line that was maintained underthe standard cell proliferation conditions (37° C., 5% carbon dioxide insterile air). Hemocytometer counted cells suspended in Hanks medium(Gibco, Grand Island N.Y.) were implanted S.C. (10⁶ cells in 0.4 mL pertumor volume determined using the equation (length)(width)²/2. The testcompounds (1.0 microM) were injected I.P. on day 1,3, and 7 using thefollowing media: control. 5% dextrose in water (D5W), triangles; taxol,suspended in Cremaphor/D5W (5/95, 18.0 mg/kg of animal weight),diamonds; and taxol-2′-MPT, dissolved in D5W (23.9 mg/kg of animalwight), dots. The procedures used for the maintenance of tumors and theexperimental details were according to protocols set forth by theDevelopmental Therapeutics Program, National Cancer Institute, viz.,National Cancer Institute Cancer Chemotherapy Reports, 3 (1972).

Mechanisms of taxol release

The mechanism of acid catalyzed taxol (1) release from taxol-2′-MPT isillustrated in Scheme 2.

However, the release of taxol from taxol-2′-MPT can also be catalyzed byserum protein and by proteins having nucleophilic groups. When contactedwith serum protein, taxol-2′-MPT is observed to displace its MPT groupand form a protein:taxol intermediate. Dialysis of the protein:taxolintermediate indicates a dissociation period of hours or days.Displacement of the MPT group by serum proteins seems to be specific forsuch serum proteins. Tested non-serum proteins seemed to lack thisactivity. In particular, immunoglobulins and serum albumen seem to beparticularly effective displacing the MPT group and formingprotein:taxol intermediates. The precise nature of the bonding betweenthe protein and taxol has not been characterized. Scheme 2 illustratesalternative pathways for MPT release.

Discussion

Taxol-2′-MPT has proven to be a remarkably stable compound in mostaqueous media. It is probable that this stability is conferred upon 2 bythe facile formation of supramolecular aggregates, a process that isprobably driven by the amphiphillic nature of the compound. Thestability, water solubility, and lack of cytotoxicity of taxol-2′-MPTmakes this class of compound an ideal a prodrug for taxol and memeticsof taxol. While essentially completely stable in aqueous media atphysiological pH and ion strength, the compound rapidly discharges taxolin sera. This profile is ideal for a clinically useful prodrug to taxol.It is possible that these properties should allow the formulation oftaxol-2′-MPT (2) without the use of Cremaphor™ or ethanol.

Synthetic Methods

Preparation of 7-TES deacetylbaccatin III (4)

7-TES deacetylbaccatin III (4). To a solution of 10-deacetylbaccatin III(3, 3.0 g, 5.51 mnol, Indena Corpation, Italy) in pyridine (250 mL) wasadded chlorotriethylsilane (18.5 mL, 110 mmol) dropwise. The resultingsolution was strirred at 25° C. for 17 hours. After dilution withdiethylether (750 mL), the solution was washed with aqueous CuSO₄ (3×200mL) and brine (200 mL). The organic layer was dried (MgSO₄),concentrated, and purified by flash chromatography (silica, 35→50%ethylacetate in petroleum ether) to give alcohol 4 (3.39 g, 91%) as awhite solid.

Physical Data for 7-TES deacetylbaccatin III (4). R_(f)0.32 (silica, 50%ethylacetate in hexanes); IR (thin film) v_(max) 3464, 2954, 2282, 1710,1453, 1362, 1271, 1242, 1105, 994 cm⁻¹; ¹H NMR (500 MHz, CDCl₃) δ8.06(dd, J=8.0, 0.9 Hz, 2 H, Bz), 7.57 (t, J=7.9 Hz, 1 H, Bz), 7.44 (t,J=7.9 Hz, 2 H, Bz), 5.56 (d, J=7.0 Hz, 1 H, 2-H), 5.14 (d, J=1.9 Hz, 1H, 10-H), 4.92 (d, J=9.5 Hz, 1 H, 5-H), 4.84-4.78 (m, 1 H, 13-H), 4.37(dd, J=10.6, 7.0 Hz, 1 H, 7-H), 4.27 (d, J=8.5 Hz, 1 H, 20-H), 4.25 (d,J=1.9 Hz, 1 H, 10-OH), 4.12 (d, J=8.5 Hz, 1 H, 20-H), 3.91 (d, J=7.0 Hz,1 H, 3-H), 2.48-2.40 (m, 1 H, 6-H), 2.25 (s, 3 H, Me), 2.25-2.17 (m, 2H, 14-CH₂), 2.04 (s, 3 H, Me), 1.90-1.82 (m, 1 H, 6-H), 1.70 (s, 3 H,Me), 1.03 (s, 6 H, Me, Me), 0.90 (t, J=8 Hz, 9 H, Si(CH₂CH₃)₃),0.58-0.42 (band, 6 H, Si(CH₂CH₃)₃); ¹³C NMR (125 MHz, CDCl₃) δ210.3,170.8, 167.0, 141.8, 135.1, 133.6, 130.1, 129.4, 128.6, 84.2, 80.7,78.8, 76.5, 74.8, 74.6, 72.9, 67.9, 57.9, 47.0, 42.7, 38.6, 37.2, 26.8,22.6, 19.5, 15.2, 9.9, 6.7, 5.1; FAB HRMS (NBA/CsI) m/e 791.2251, M+Cs⁺calcd for C₃₅H₅₀O₁₀Si 791.2228.

Preparation of enone 5

Enone 5. To a solution of 7-TES deacetylbaccatin III (4, 1.5 g, 2.28mmol) and 4-methylmorpholine N-oxide (NMO, 240 mg, 2.05 mmol) in CH₂Cl₂(5 mL) was added 4 Å molecular sieves (200 mg) and the suspension wasstirred at 25° C. for 10 minutesutes. A catalytic amount oftetrapropylammonium perruthenate from Aldrich Chemical Company Inc.(TPAP, 40 mg, 0.11 mmol) was added by portions and the reaction mixturewas stirred at 25° C. for 0.5 hours. Small amounts of 4-methylmorpholineN-oxide and TPAP were added alternatively at 0.5 hour intervals untilthe starting material was consumed to the extent of ca. 95% by TLC. Thereaction mixture was filtered through silica gel, eluted with CH₂Cl₂(100 mL), and concentrated to give enone 5 (1.44 g, 96%) as a whitesolid.

Physical Data for Enone 5. R_(f)=0.5 (silica, 50% ethylacetate inhexanes); IR (thin film) v_(max) 3446, 2957, 2882, 1726, 1672, 1456,1367, 1243, 1106 cm⁻¹; ¹H NMR (500 MHz, CDCl₃) δ8.05 (dd,J=8.0, 1.0 Hz,2 H, Bz), 7.61 (t,J=7.5 Hz, 1 H, Bz), 7.45 (t,J=7.5 Hz, 2 H, Bz), 5.63(d,J=7.5 Hz, 1 H, 2-H), 5.30 (d,J=2.0 Hz, 1 H, 10-H), 4.90 (d, J=8.0 Hz,1 H, 5-H), 4.36 (dd, J=10.5, 7.0 Hz, 1 H, 7-H), 4.31 (d, J=8.5 Hz, 1 H,20-H), 4.30 (d, J=2.0 Hz, 1 H, 10-OH), 4.11 (d, J=8.5 Hz, 1 H, 20-H),3.93 (d, J=7.5 Hz, 1 H, 3-H), 2.92 (d, J=19.5 Hz, 1 H, 14-H), 2.62 (d,J=19.5 Hz, 1 H, 14-H), 2.50-2.42 (m, 1 H, 6-H), 2.17 (s, 3 H, Me), 2.08(s, 3 H, Me), 1.90-1.82 (m, 1 H, 6-H), 1.77 (s, 1 H, 1-OH), 1.70 (s, 3H, Me), 1.21 (s, 3 H, Me), 1.14 (s, 3 H, Me), 0.90 (t, J=8.0 Hz, 9 H,Si(CH₂CH₃)₃), 0.60-0.42 (band, 6 H, Si(CH₂CH₃)₃); ¹³C NMR (125 MHz,CDCl₃) δ208.2, 198.1, 170.2, 166.8, 156.6, 139.1, 134.0, 130.0, 128.8,128.8, 84.0, 80.4, 78.5, 76.2, 75.7, 72.9, 72.8, 58.8, 45.9, 43.4, 42.5,37.2, 33.0, 21.7, 17.5, 13.6, 9.6, 6.7, 5.1; FAB HRMS (NBA/NaI) m/e657.3070, M+Na⁺ calcd for C₃₅H₄₈O₁₀Si 657.3095.

Preparation of triol 6

Triol 6. To a solution of enone 5 (1.44 g, 2.19 mmol) in MeOH (300 mL)at 0° C. was slowly added an aqueous solution of K₂CO₃ (3.0 g in 32 mLof H₂O). The solution was stirred at 0° C. for 2.5 hours. The reactionwas then quenched with aqueous NH₄Cl (150 mL) and the resulting mixturewas extracted with CH₂Cl₂ (2×200 mL). The organic layer was dried(Na₂SO₄), concentrated, and purified by flash chromatography (silica,35→50% ethylacetate in petroleum ether) to give enone 5 (270 mg, 19%)and triol 6 (912 mg, 93% based on 81% conversion).

Physical Data for Triol 6. R_(f)=0.24 (silica, 50% ethylacetate inhexanes); IR (thin film) v_(max) 3414, 2957, 2881, 1727, 1664, 1370cm⁻¹; ¹H NMR (500 MHz, CDCl₃) δ5.23 (d, J=9.5 Hz, 1 H, 10-H), 4.89 (d,J=9.5 Hz, 1 H, 5-H), 4.63 (d, J=9.5 Hz, 1 H, 20-H), 4.56 (d, J=9.5 Hz, 1H, 20-H), 4.32 (dd, J=11.0, 7.0 Hz, 1 H, 7-H), 4.28 (d, J=2.5 Hz, 1 H,10-OH), 3.89 (dd, J=6.5, 4.0 Hz, 1 H, 2-H), 3.57 (d, J=6.5 Hz, 1 H,3-H), 2.78 (d, J=19.5 Hz, 1 H, 14-H), 2.58 (d, 4.0 Hz, 1 H, 2-OH), 2.52(d, J=19.5 Hz, 1 H, 14-H), 2.49-2.42 (m, 1 H, 6-H), 2.03 (s, 3 H, Me),1.92-1.84 (m, 1 H, 6-H), 1.68 (s, 3 H, Me), 1.21 (s, 3 H, Me), 1.04 (s,3 H, Me), 0.90 (t, J=8.0 Hz, 9 H, Si(CH₂CH₃)₃), 0.60-0.40 (band, 6 H,Si(CH₂CH₃)₃); ¹³C NMR (125 MHz, CDCl₃) δ208.9, 198.5, 170.1, 156.7,138.8, 83.8, 81.2, 77.6, 75.7, 72.8, 72.5, 58.8, 45.8, 43.1, 42.8, 37.3,32.7, 21.6, 17.5, 13.6, 9.7, 6.7, 5.1; FAB HRMS (NBA/NaI) m/e 575.2648,M+Na⁺ calcd for C₂₈H₄₄O₉Si 575.2652.

Preparation of Carbonate 7

Carbonate 7. A solution of triol 6 (60.0 mg, 0.109 mmol) in THF (2 mL)was treated with carbonyldiimidazole (110.0 mg, 0.678 mmol) and stirredat 40° C. for 0.5 hour The reaction mixture was concentrated andredisolved in THF (5 mL). TLC analysis confirmed total consumption ofstarting material. 1 N aqueous HCl (5 mL) was added and the resultingsolution was allowed to stir for 15 minutes at 25° C. diethylether (25mL) was added, the organic layer was separated, washed with aqueousNaHCO₃ (10 mL) and brine (10 mL), dried (MgSO₄), and concentrated togive carbonate 7 (58 mg, 93%) as a white foam.

Physical Data for Carbonate 7. R_(f)=0.50 (silica, 35% ethylacetate inhexanes); IR (thin film) v_(max) 3438, 2957, 2882, 1820, 1731, 1685,1370, 1236 cm⁻¹; ¹H NMR (500 MHz, CDCl₃) δ5.27 (d, J=2.5 Hz, 1 H, 10-H),4.89 (d, J=9.0 Hz, 1 H, 5-H), 4.60 (d, J=9.0 Hz, 1 H, 20-H), 4.45 (d,J=9.0 Hz, 1 H, 20-H), 4.43 (d, J=6.0 Hz, 1 H, 2-H), 4.33 (dd, J=10.0,7.5 Hz, 1 H, 7-H), 4.28 (d, J=2.5 Hz, 1 H, 10-OH), 3.54 (d, J=6.0 Hz, 1H, 3-H), 2.88 (d, J=20.0 Hz, 1 H, 14-H), 2.75 (d, J=20.0 Hz, 1 H, 14-H),2.54-2.47 (m, 1 H, 6-H), 2.08 (s, 3 H, Me), 2.06 (s, 3 H, Me), 1.92-1.84(m, 1 H, 6-H), 1.77 (s, 3 H, Me), 1.31 (s, 3 H, Me), 1.15 (s, 3 H, Me),0.88 (t, J=8.5 Hz, 9 H, Si(CH₂CH₃)₃), 0.55-0.45 (band, 6 H,Si(CH₂CH₃)₃); ¹³C NMR (125 MHz, CDCl₃) δ208.4, 195.5, 170.5, 154.0,152.0, 141.2, 88.4, 83.9, 79.8, 79.0, 76.7, 75.7, 71.9, 60.3, 43.0,41.6, 39.8, 37.7, 31.6, 21.5, 17.8, 14.4, 9.7, 6.6, 5.0;

FAB HRMS (NBA) m/e 579.2652, M+H⁺ calcd for C₂₉H₄₂O₁₀Si 579.2626.

Preparation of n Butyl-C-2 ester derivative (Alcohol 8)

Alcohol 8. A solution of carbonate 7 (10 mg, 0.0173 mmol) intetrahydrofuran (1 mL) at −78° C. was treated with n-Butyllithium fromAldrich Chemical Company, Inc. (0.087 mL of a 1.6 M solution in hexanes,0.139 mmol) and stirred for 1.0 hour The reaction mixture was pouredinto a mixture of diethylether (10 mL) and aqueous NH₄Cl (5 mL). Theorganic layer was separated and the aqueous layer was extracted withdiethylether (2×5 mL). The combined organic layer was washed with asaturated solution of brine (5 mL), dried (MgSO₄), concentrated, andpurified by flash chromatography (silica, 35→50% ethylacetate inhexanes) to give 8 (7.9 mg, 72%) as an amorphous solid.

Physical Data for Alcohol 8. R_(f)=0.36 (silica, 35% ethylacetate inpetroleum ether); IR (film) v_(max) 3437, 2962, 2865, 1726, 1671, 1367,1239, 1105 cm⁻¹; ¹H NMR (500 MHz, CDCl₃) δ5.36 (d, J=6.5 Hz, 1 H, 2-H),5.26 (d, J=2.5 Hz, 1 H, 10-H), 4.89 (br d, J=8.0 Hz, 1 H, 5-H), 4.47 (d,J=8.0 Hz, 1 H, 20-H), 4.32 (dd, J=10.5, 6.5 Hz, 1 H, 7-H), 4.26 (d,J=2.5 Hz, 1 H, 10-OH), 4.15 (d, J=8.0 Hz, 1 H, 20-H), 3.81 (d, J=6.5 Hz,1 H, 3-H), 2.73 (d, J=20.0 Hz, 1 H, 14-H), 2.57 (d, J=20.0 Hz, 1 H,14-H), 2.49-2.41 (m, 1 H, 6-H), 2.38-2.23 (m, 2 H, OCCH₂CH₂)₂CH₃), 2.06(s, 3 H, Me), 2.04 (s, 3 H, Me), 1.90-1.82 (m, 1 H, 6-H), 1.67 (s, 1 H,OH), 1.64 (s, 3 H, Me), 1.68-1.52 (m, 2 H, OCCH₂CH₂CH₂CH₃), 1.41-1.30(m, 2 H, OC(CH₂)₂CH₂CH₃), 1.19 (s, 3 H, Me), 1.07 (s, 3 H, Me),0.94-0.86 (band, 12 H, CH₃ of Bu, OSi(CH₂CH₃)₃), 0.58-0.45 (band, 6 H,OSi(CH₂CH₃)₃); FAB HRMS (NBA) m/e 637.3421, M+H⁺ calcd for C₃₃H₅₂O₁₀Si637.3408.

Preparation of vinyl-C-2 ester derivative (Alcohols 9 and 10)

Alcohols 9 and 10. A solution of carbonate 7 (111.3 mg, 0.192 mmol) intetrahydrofuran (2 mL) at −78° C. was treated with vinyllithium (3.7 mLof a 0.52 M solution in diethylether, 1.92 mmol, prepared fromtetravinyltin and nButyllithium: methodology from Wakefield, B. J.Organolithium Methods, Academic Press: London, 1988, p. 46) and stirredfor 2.25 hour. The reaction mixture was poured into a mixture of CH₂Cl₂(20 mL) and aqueous NH₄Cl (10 mL), the organic layer was separated, andthe aqueous layer was extracted with CH₂Cl₂ (3×10 mL). The combinedorganic layer was washed with brine (15 mL), dried (MgSO₄),concentrated, and purified by flash chromatography (silica, 30→50%ethylacetate in petroleum ether) to give 9 (60.0 mg, 52%), and 10 (25.7mg, 24% ) as white foams.

Physical Data for Alcohol 9. R_(f)=0.52 (silica, 50% ethylacetate inhexanes); IR (film) v_(max) 3442, 2956, 2882, 1727, 1672, 1407, 1368,1243, 1182, 1110, 1050, 986, 826, 736 cm⁻¹; ¹H NMR (500 MHz, CDCl₃)δ6.51 (dd, J=17.0, 1.0 Hz, 1 H, vinyl H), 6.13 (dd, J=17.0, 10.5 Hz, 1H, vinyl H), 6.00 (dd, J=10.5, 1.0 Hz, 1 H, vinyl H), 5.45 (br d, J=6.5Hz, 1 H, 2-H), 5.30 (d, J=2.5 Hz, 1 H, 10-H), 4.91 (br d, J=9.5 Hz, 1 H,5-H), 4.44 (d, J=8.5 Hz, 1 H, 20-H), 4.35 (dd, J=10.5, 6.5 Hz, 1 H,7-H), 4.30 (d, J=2.5 Hz, 1 H, 10-OH), 4.14 (d, J=8.5 Hz, 1 H, 20-H),3.88 (d, J=6.5 Hz, 1 H, 3-H), 2.79 (d, J=20.0 Hz, 1 H, 14-H), 2.61 (d,J=20.0 Hz, 1 H, 14-H), 2.48 (ddd, J=14.5, 9.5, 6.5 Hz, 1 H, 6-H), 2.09(s, 3 H, Me), 2.08 (s, 3H, Me), 1.89 (ddd, J=14.5, 10.5, 2.0 Hz, 1 H,6-H), 1.72 (s, 1 H, OH), 1.68 (s, 3 H, Me), 1.22 (s, 3 H, Me), 1.12 (s,3 H, Me), 0.92 (t, J=8.0 Hz, 9 H, OSi(CH₂CH₃)₃), 0.62-0.46 (band, 6 H,OSi(CH₂CH₃)₃); FAB HRMS (NBA/CsI) m/e 739.1925, M+Cs⁺ calcd forC₃₁H₄₆O₁₀Si 739.1915.

Physical Data for Alcohol 10. R_(f)=0.24 (silica, 50% ethylacetate inhexanes); IR (film) v_(max) 3439, 2955, 2881, 1711, 1671, 1409, 1365,1188, 1115, 980, 833, 735 cm⁻¹; ¹H NMR (500 MHz, CDCl₃) δ6.48 (br d,J=17.0 Hz, 1 H, vinyl H), 6.10 (dd, J=17.0, 10.5 Hz, 1 H, vinyl H), 5.97(br d, J=10.5 Hz, 1 H, vinyl H), 5.47 (br d, J=6.0 Hz, 1 H, 2-H), 5.25(d, J=2.5 Hz, 1 H, 10-H), 4.75 (dd, J=9.5, 3.5 Hz, 1 H, 5-H), 4.38 (d,J=8.5 Hz, 1 H, 20-H), 4.30 (d, J=2.5 Hz, 1 H, 10-OH), 4.24 (d, J=8.5 Hz,1 H, 20-H), 3.90 (dd, J=11.5, 6.0 Hz, 1 H, 7-H), 3.28 (d, J=19.5 Hz, 1H, 14-H), 3.24 (d, J=6.0 Hz, 1 H, 3-H), 3.06 (br s, 1 H, OH), 2.58 (d,J=19.5 Hz, 1 H, 14-H), 2.38 (ddd, J=14.5, 9.5, 6.0 Hz, 1 H, 6-H), 2.07(s, 3 H, Me), 1.98 (ddd, J=14.5, 11.5, 3.5 Hz, 1 H, 6-H), 1.87 (s, 1 H,OH), 1.61 (s, 3 H, Me), 1.23 (s, 3 H, Me), 1.13 (s, 3 H, Me), 0.90 (t,J=8.0 Hz, 9 H, OSi(CH₂CH₃)₃), 0.59-0.45 (band, 6 H, OSi(CH₂CH₃)₃); FABHRMS (NBA/CsI) m/e 697.1802, M+Cs⁺ calcd for C₂₉H₄₄O₉Si 697.1809.

Preparation of 2-Furyl-C-2 ester derivative (Alcohol 11)

Alcohol 11. A solution of carbonate 7 (46 mg, 0.0795 mmol) intetrahydrofuran (3 mL) at −78° C. was treated with 2-furyllithium (4 mLof a 0.47 M suspension in diethylether, 1.88 mmol, prepared from furan(Aldrich Chemical Company, Inc.) and n-Butyllithium (Aldrich ChemicalCompany, Inc.); methodology from Ramanathan, V.; Levine, R. J. Org.Chem. 1962, 27, 1216) and stirred for 10 minutesutes. The reactionmixture was poured into a mixture of CH₂Cl₂ (15 mL) and aqueous NH₄Cl(20 mL). The organic layer was separated and the aqueous layer wasextracted with CH₂Cl₂ (2×10 mL). The combined organic layer was washedwith brine (10 mL), dried (MgSO₄) and concentrated to give 11 which wastaken into the next step without further purification.

Physical Data for Alcohol 11. R_(f)=0.38 (silica, 20% ethylacetate inpetroleum ether); IR (film) v_(max) 3442, 2956, 2882, 1727, 1672, 1468,1300, 1240, 1110, 1007, 733 cm⁻¹; ¹H NMR (500 MHz, CDCl₃) δ7.66-7.64 (m,1 H, furan), 7.24 (br d, J=3.5 Hz, 1 H, furan), 6.58 (dd, J=3.5, 1.5 Hz,1 H, furan), 5.55 (d, J=6.5 Hz, 1 H, 2-H), 5.31 (d, J=2.0 Hz, 1 H,10-H), 4.92 (br d, J=9.0 Hz, 1 H, 5-H), 4.43 (d, J=8.5 Hz, 1 H, 20-H),4.37 (dd, J=10.5, 6.5 Hz, 1 H, 7-H), 4.32 (d, J=2.0 Hz, 1 H, 10-OH),4.18 (d, J=8.5 Hz, 1 H, 20-H), 3.93 (d, J=6.5 Hz, 1 H, 3-H), 2.88 (d,J=20.0 Hz, 1 H, 14-H), 2.63 (d, J=20.0 Hz, 1 H, 14-H), 2.55-2.37 (m, 1H, 6-H), 2.15 (s, 3 H, Me), 2.09 (s, 3 H, Me), 1.93-1.87 (m, 1 H, 6-H),1.81 (s, 1 H, OH), 1.71 (s, 3 H, Me), 1.23 (s, 3 H, Me), 1.15 (s, 3 H,Me), 0.93 (t, J=8.0 Hz, 9 H, OSi(CH₂CH₃)₃), 0.62-0.42 (band, 6 H,OSi(CH₂CH₃)₃); FAB HRMS (NBA/NaI) m/e 669.2717, M+Na⁺ calcd forC₃₃H₄₆O₁₁Si 669.2707.

Preparation of 2-thiophenyl-C-2 ester derivative (Alcohol 12)

Alcohol 12. A solution of carbonate 7 (50.0 mg, 0.0864 mmol) intetrahydrofuran (5 mL) at −78° C. was treated with 2-thienyllithium fromAldrich Chemical Company, inc. (1.30 mL of a 1.0 M solution intetrahydrofuran, 1.30 mmol) and stirred for 0.5 hour. The reactionmixture was poured into a mixture of diethylether (10 mL) and aqueousNH₄Cl (5 mL). The organic layer was separated and the aqueous layer wasextracted with diethylether (2×10 mL). The combined organic layer waswashed with brine (10 mL), dried (MgSO₄), concentrated, and purified byflash chromatography (silica, 10→35% ethylacetate in hexanes) to give 7(16.5 mg, 33%), 12 (36.8 mg, 96% based on 67% conversion) as anamorphous solid.

Physical Data for Alcohol 12. R_(f)=0.56 (silica, 50% ethylacetate inhexanes); IR (film) v_(max) 3403, 2945, 2881, 1717, 1669, 1520, 1413,1360, 1248, 1078; ¹H NMR (500 MHz, CDCl₃) δ7.84 (dd, J=3.5, 1.0 Hz, 1 H,thiophene), 7.64 (d, J=1.0, 5.0 Hz, 1 H, thiophene), 7.14 (dd, J=5.0,3.5 Hz, 1 H, thiophene), 5.53 (br d, J=6.5 Hz, 1 H, 2-H), 5.29 (d, J=2.5Hz, 1 H, 10-H), 4.90 (br d, J=7.5 Hz, 1 H, 5-H), 4.44 (d, J=8.5 Hz, 1 H,20-H), 4.35 (dd, J=10.5 Hz, 6.5 Hz, 1 H, 7-H), 4.29 (d, J=2.5 Hz, 1 H,10-OH), 4.19 (d, J=8.5 Hz, 1 H, 20-H), 3.90 (d, J=6.5 Hz, 1 H, 3-H),2.89 (d, J=19.5 Hz, 1 H, 14-H), 2.62 (d, J=19.5 Hz, 1 H, 14-H),2.49-2.43 (m, 1 H, 6-H), 2.15 (s, 3 H, Me), 2.07 (s, 3 H, Me), 1.92-1.84(m, 1 H, 6-H), 1.73 (s, 1 H, OH), 1.71 (s, 3 H, Me), 1.21 (s, 3 H, Me),1.13 (s, 3 H, Me), 0.91 (t, J=8.0 Hz, 9 H, OSi(CH₂CH₃)₃), 0.56-0.49(band, 6 H, OSi(CH₂CH₃)₃); FAB HRMS (NBA) m/e 663.2655, M+H⁺ calcd forC₃₃H₄₆O₁₀SSi 663.2659.

Preparation of 3-thiophenyl-C-2 ester derivatives (Alcohol 13 and 14)

Alcohols 13 and 14. A solution of carbonate 7 (107.9 mg, 0.186 mmol) intetrahydrofuran (6.2 mL) at −78° C. was treated with 3-thienyllithium(2.76 mL of a 0.41 M solution in diethylether tetrahydrofuran:hexanes(4.5:1:2), 1.13 mmol, prepared from 3-bromothiophene and n-Butyllithium;methodology from Camici, L.; Ricci, A.; Taddei, M. Tetrahedron Lett.1986, 27, 5155) and stirred for 1.5 hour The reaction mixture was pouredinto a mixture of CH₂Cl₂ (15 mL) and aqueous NH₄Cl (20 mL), the organiclayer was separated, and the aqueous layer was extracted with CH₂Cl₂(2×10 mL). The combined organic layer was washed with brine (10 mL),dried (MgSO₄), concentrated, and purified by flash chromatography(silica, 20→30% ethylacetate in hexanes) to give 7 (16.9 mg, 16%), 13(87.0 mg, 83% based on 84% conversion), and hydrolyzed C4 acetate 14(C4-hydrolyzed side product, 9.7 mg, 10% based on 84% conversion) asamorphous solids.

Physical Data for Alcohol 13. R_(f)=0.74 (silica, 50% ethylacetate inhexanes), 0.41 (silica, 10% ethylacetate in benzene, 3 elutions); IR(thin film) v_(max) 3442, 3110, 2956, 2882, 1725, 1672, 1410, 1368,1244, 1198, 1101, 988, 825, 744 cm⁻¹; ¹H NMR (500 MHz, CDCl₃) δ8.18 (dd,J=3.0, 1.2 Hz, 1 H, thiophene), 7.54 (dd, J=5.0, 1.2 Hz, 1 H,thiophene), 7.37 (dd, J=5.0, 3.0 Hz, 1 H, thiophene), 5.56 (dd, J=6.5,1.0 Hz, 1 H, 2-H), 5.31 (d, J=2.5 Hz, 1 H, 10-H), 4.92 (dd, J=7.5, 2.0Hz, 1 H, 5-H), 4.40-4.34 (m, 2 H, 20-H, 7-H), 4.31 (d, J=2.5 Hz, 1 H,10-OH), 4.15 (d, J=8.5 Hz, 1 H, 20-H), 3.93 (d, J=6.5 Hz, 1 H, 3-H),2.88 (d, J=20 Hz, 1 H, 14-H), 2.63 (dd, J=20.0, 1.0 Hz, 1 H, 14-H), 2.47(ddd, J=14.5, 9.5, 6.5 Hz, 1 H, 6-H), 2.18 (s, 3 H, Me), 2.10 (s, 3 H,Me), 1.89 (ddd, J=14.5, 10.5, 2.0 Hz, 1 H, 6-H), 1.81 (br s, 1 H, OH),1.72 (s, 3 H, Me), 1.23 (s, 3 H, Me), 1.15 (s, 3 H, Me), 0.93 (t, J=8.0Hz, 9 H, OSi(CH₂CH₃)₃), 0.62-0.48 (band, 6 H, Si(CH₂CH₃)₃); FAB HRMS(NBA/CsI) m/e 795.1640, M+Cs⁺ calcd for C₃₃H₄₆O₁₀SSi 795.1635.

Physical Data for Alcohol 14: R_(f)=0.54 (silica, 50% ethylacetate inhexanes); IR (thin film) v_(max) 3437, 3108, 2955, 2880, 1709, 1674,1605, 1520, 1410, 1360, 1258, 1194, 1103, 1004, 829, 744 cm⁻¹; ¹H NMR(500 MHz, CDCl₃) δ8.15 (dd, J=3.0, 1.0 Hz, 1 H, thiophene), 7.49 (dd,J=5.0, 1.0 Hz, 1 H, thiophene), 7.35 (dd, J=5.0, 3.0 Hz, 1 H,thiophene), 5.59 (d, J=6.0 Hz, 1 H, 2-H), 5.27 (d, J=2.5 Hz, 1 H, 10-H),4.73 (dd, J=9.5, 3.5 Hz, 1 H, 5-H), 4.40 (d, J=8.5 Hz, 1 H, 20-H), 4.32(d, J=2.5 Hz, 1 H, 10-OH), 4.15 (d, J=8.5 Hz, 1 H, 20-H), 3.92 (dd,J=11.5, 6.0 Hz, 1 H, 7-H), 3.44 (d, J=19.5 Hz, 1 H, 14-H), 3.30 (d,J=6.0 Hz, 1 H, 3-H), 2.91 (br s, 1 H, OH), 2.61 (d, J=19.5 Hz, 1 H,14-H), 2.38 (ddd, J=14.5, 9.5, 6.0 Hz, 1 H, 6-H), 2.09 (s, 3 H, Me),1.99 (ddd, J=14.5, 11.5, 3.5 Hz, 1 H, 6-H), 1.81 (br s, 1 H, OH), 1.65(s, 3 H, Me), 1.24 (s, 3 H, Me), 1.16 (s, 3 H, Me), 0.91 (t, J=8.0 Hz, 9H, OSi(CH₂CH₃)₃), 0.60-0.46 (band, 6 H, OSi(CH₂CH₃)₃); FAB HRMS(NBA/CsI) m/e 753.1530, M+Cs⁺ calcd for C₃₁H₄₄O₉SSi 753.1530.

Preparation of 2-pyridinyl-C-2 ester derivatives (Alcohol 15, 16 andtriol 6)

Alcohol 15 and 16, and triol 6. A solution of carbonate 7 (62.6 mg,0.108 mmol) in tetrahydrofuran (5.4 mL) at −78° C. was treated with2-lithiopyridine (1.15 mL of a 0.44 M solution in diethylether-pentane1:1, 0.506 mmol, prepared from 2-bromopyridine and t-Butyllithium;methodology from Malmberg, H.; Nilsson, M. Tetrahedron, 1986, 42, 3981)and stirred for 1.3 hour The reaction mixture was poured into a mixtureof ethylacetate (10 mL) and aqueous NH₄Cl (5 mL), the organic layer wasseparated, and the aqueous layer was extracted with ethylacetate (2×10mL). The combined organic layer was washed with brine (5 mL), dried(MgSO₄), concentrated, and purified by flash chromatography (silica,70→100% ethylacetate in petroleum ether) to give 6 (16.3 mg, 27%), 15(28.0 mg, 39%), and 16 (8.4 mg, 13%) as amorphous solids.

Physical Data for Alcohol 15. R_(f)=0.60 (silica, ethylacetate); ¹H NMR(500 MHz, CDCl₃) δ8.77 (ddd, J=4.5, 1.7, 1.0 Hz, 1 H, pyridine), 8.05(br d, J=7.5 Hz, 1 H, pyridine), 7.89 (ddd, J=7.5, 7.5, 1.7 Hz, 1 H,pyridine), 7.53 (ddd, J=7.5, 4.5, 1.0 Hz, 1 H, pyridine), 5.61 (dd,J=6.5, 1.0 Hz, 1 H, 2-H), 5.33 (d, J=2.5 Hz, 1 H, 10-H), 4.92 (dd,J=9.5, 2.0 Hz, 1 H, 5-H), 4.39 (dd, J=10.5, 6.5 Hz, 1 H, 7-H), 4.36 (d,J=9.0 Hz, 1 H, 20-H), 4.33 (d, J=2.5 Hz, 1 H, 10-OH), 4.28 (d, J=9.0 Hz,1 H, 20-H), 3.96 (d, J=6.5 Hz, 1 H, 3-H), 2.98 (d, J=20.0 Hz, 1 H,14-H), 2.71 (dd, J=20.0, 1.0 Hz, 1 H, 14-H), 2.50 (s, 1 H, OH), 2.48(ddd, J=14.5, 9.5, 6.5 Hz, 1 H, 6-H), 2.15 (s, 3 H, Me), 2.11 (s, 3 H,Me), 1.90 (ddd, J=14.5, 10.5, 2.0 Hz, 1 H, 6-H), 1.76 (s, 3 H, Me), 1.24(s, 3 H, Me), 1.16 (s, 3 H, Me), 0.93 (t, J=8.0 Hz, 9 H, OSi(CH₂CH₃)₃),0.63-0.47 (band, 6 H, OSi(CH₂CH₃)₃); FAB HRMS (NBA/CsI) m/e 790.2060,M+Cs⁺ calcd for C₃₄H₄₇O₁₀NSi 790.2024.

Physical Data for Alcohol 16. R_(f)=0.45 (silica, ethylacetate); IR(film) v_(max) 3435, 2954, 2879, 1732, 1674, 1589, 1362, 1305, 1241,1116, 998, 829, 741 cm⁻¹; ¹H NMR (500 MHz, CDCl₃) δ8.73 (br d, J=4.5 Hz,1 H, pyridine), 8.15 (br d, J=7.5 Hz, 1 H, pyridine), 7.90 (ddd, J=7.5,7.5, 1.7 Hz, 1 H, pyridine), 7.56 (ddd, J=7.5, 4.5, 1.0 Hz, 1 H,pyridine), 5.53 (dd, J=7.5, 1.0, 1 H, 2-H), 5.30 (d, J=2.5 Hz, 1 H,10-H), 4.84 (dd, J=9.5, 3.0 Hz, 1 H, 5-H), 4.81 (br s, 1 H, OH), 4.31(d, J=2.5 Hz, 1 H, 10-OH), 4.25 (s, 2 H, 20-CH₂), 3.97 (dd, J=11.5, 6.5Hz, 1 H, 7-H), 3.31 (d, J=19.5 Hz, 1 H, 14-H), 3.23 (d, J=7.5 Hz, 1 H,3-H), 2.57 (br d, J=19.5 Hz, 1 H, 14-H), 2.43 (ddd, J=14.5, 9.5, 6.5 Hz,1 H, 6-H), 2.11 (s, 3 H, Me), 1.95 (ddd, J=14.5, 11.5, 3.0 Hz, 1 H,6-H), 1.92 (br s, 1 H, OH), 1.70 (s, 3 H, Me), 1.24 (s, 3 H, Me), 1.17(s, 3 H, Me), 0.91 (t, J=8.0 Hz, 9 H, OSi(CH₂CH₃)₃), 0.60-0.46 (band, 6H, OSi(CH₂CH₃)₃).

Physical Data for Triol 6. R_(f)=0.24 (silica, 50% ethylacetate inhexanes); IR (thin film) v_(max) 3414, 2957, 2881, 1727, 1664, 1370cm⁻¹; ¹H NMR (500 MHz, CDCl₃) δ5.23 (d, J=9.5 Hz, 1 H, 10-H), 4.89 (d,J=9.5 Hz, 1 H, 5-H), 4.63 (d, J=9.5 Hz, 1 H, 20-H), 4.56 (d, J=9.5 Hz, 1H, 20-H), 4.32 (dd, J=11.0, 7.0 Hz, 1 H, 7-H), 4.28 (d, J=2.5 Hz, 1 H,10-OH), 3.89 (dd, J=6.5, 4.0 Hz, 1 H, 2-H), 3.57 (d, J=6.5 Hz, 1 H,3-H), 2.78 (d, J=19.5 Hz, 1 H, 14-H), 2.58 (d, 4.0 Hz, 1 H, 2-OH), 2.52(d, J=19.5 Hz, 1 H, 14-H), 2.49-2.42 (m, 1 H, 6-H), 2.03 (s, 3 H, Me),1.92-1.84 (m, 1 H, 6-H), 1.68 (s, 3 H, Me), 1.21 (s, 3 H, Me), 1.04 (s,3 H, Me), 0.90 (t, J=8.0 Hz, 9 H, Si(CH₂CH₃)₃), 0.60-0.40 (band, 6 H,Si(CH₂CH₃)₃); ¹³C NMR (125 MHz, CDCl₃) δ208.9, 198.5, 170.1, 156.7,138.8, 83.8, 81.2, 77.6, 75.7, 72.8, 72.5, 58.8, 45.8, 43.1, 42.8, 37.3,32.7, 21.6, 17.5, 13.6, 9.7, 6.7, 5.1; FAB HRMS (NBA/NaI) m/e 575.2648,M+Na⁺ calcd for C₂₈H₄₄O₉Si 575.2652.

Preparation of 3-pyridinyl-C-2 ester derivative (Alcohol 17)

Alcohol 17. To a solution of 3-lithiopyridine (1.15 mmol) intetrahydrofuran (7 mL), prepared from 3-bromopyridine (Aldrich ChemicalCompany Inc.) and n-Butyllithium (Aldrich Chemical Company Inc.) at−100° C. (methodology from Parham, W. E.; Piccirilli, R. M. J. Org.Chem. 1977, 42, 257), was added a solution of carbonate 7 (133.1 mg,0.230 mmol) in tetrahydrofuran (2 mL) via cannula. The resultingsolution was stirred for 1 h, allowed to warm to −78° C., stirred for 1h, and poured into a mixture of ethylacetate (10 mL) and aqueous NH₄Cl(10 mL). The organic layer was separated and the aqueous layer wasextracted with ethylacetate (2×10 mL). The combined organic layer waswashed with brine (10 mL), dried (MgSO₄), concentrated, and purified byflash chromatography (silica, 70→95% ethylacetate in petroleum ether) togive 7 (64.8 mg, 49%) and 17 (43.9 mg, 57% based on 51% conversion) asan amorphous solid.

Physical Data for Alcohol 17. R_(f)=0.56 (silica, ethylacetate); IR(film) v_(max) 3435, 2956, 2882, 1731, 1671, 1592, 1366, 1280, 1240,1109, 991, 824, 739 cm⁻¹; ¹H NMR (500 MHz,

CDCl₃) δ9.24 (br s, 1 H, pyridine), 8.81 (d, J=1.0, 4.5 Hz, 1 H,pyridine), 8.30 (ddd, J=8.0, 2.0, 2.0 Hz, 1 H, pyridine), 7.44 (dd,J=8.0, 4.5 Hz, 1 H, pyridine), 5.66 (d, J=6.5 Hz, 1 H, 2-H), 5.32 (s, 1H, 10-H), 4.92 (dd, J=9.5, 2.0 Hz, 1 H, 5-H), 4.38 (dd, J=10.5, 6.5 Hz,1 H, 7-H), 4.32 (br s, 1 H, OH), 4.30 (d, J=8.5 Hz, 1 H, 20-H), 4.13 (d,J=8.5 Hz, 1 H, 20-H), 3.96 (d, J=6.5 Hz, 1 H, 3-H), 2.92 (d, J=19.5 Hz,1 H, 14-H), 2.66 (d, J=19.5 Hz, 1 H, 14-H), 2.48 (ddd, J=15.5, 9.5, 6.5Hz, 1 H, 6-H), 2.18 (s, 3 H, Me), 2.10 (s, 3 H, Me), 2.03 (s, 1 H, OH),1.89 (ddd, J=14.5, 10.5, 2.0 Hz, 1 H, 6-H), 1.72 (s, 3 H, Me), 1.23 (s,3 H, Me), 1.16 (s, 3 H, Me), 0.92 (t, J=8.0 Hz, 9 H, OSi(CH₂CH₃)₃),0.62-0.48 (band, 6 H, OSi(CH₂CH₃)₃); FAB HRMS (NBA/CSI) m/e 790.2030,M+Cs⁺ calcd for C₃₄H₄₇O₁₀NSi 790.2024.

Preparation of 4-N, N-dimethylaniline-C-2 ester derivative (Alcohol 18)

Alcohol 18. A solution of carbonate 7 (150 mg, 0.259 mmol) intetrahydrofuran (20 mL) at −78° C. was treated with4-lithio-N,N-dimethylaniline (6.5 mL of a 0.39 M solution indiethylether:pentane (3:1), 2.54 mmol, prepared from4-bromo-N,N-dimethylaniline and t-Butyllithium; methodology from Jones,F. N.; Hauser, C. R. J. Org. Chem. 1962, 27, 4389) and stirred for 15minutesutes. The reaction mixture was poured into a mixture of CH₂Cl₂(35 mL) and aqueous NH₄Cl (20 mL), the organic layer was separated, andthe aqueous layer was extracted with CH₂Cl₂ (2×20 mL). The combinedorganic layer was washed with brine (20 mL), dried (MgSO₄),concentrated, and purified by flash chromatography (silica, 10→35%ethylacetate in petroleum ether) to give 18 (55.0 mg, 30%) as anamorphous solid.

Physical Data for Alcohol 18. R_(f)=0.26 (silica, 35% ethylacetate inhexanes); IR (film) v_(max) 3414, 2924, 1706, 1669, 1605, 1530, 1094; ¹HNMR (500 MHz, CDCl₃) δ7.90 (d, J=9.0 Hz, 2 H, Ar), 6.64 (d, J=9.0 Hz, 2H, Ar), 5.60 (br d, J=7.0 Hz, 1 H, 2-H), 5.29 (d, J=2.5 Hz, 1 H, 10-H),4.89 (br d, J=9.5 Hz, 1 H, 5-H), 4.37 (d, J=8.5 Hz, 1 H, 20-H), 4.36(dd, J=10.5, 6.5 Hz, 1 H, 7-H), 4.31 (d, J=2.5 Hz, 1 H, 10-OH), 4.13 (brd, J=8.5 Hz, 1 H, 20-H), 3.90 (d, J=7.0 Hz, 1 H, 3-H), 3.05 (s, 6 H,NMe₂), 2.93 (s, 1 H, OH), 2.90 (d, J=20.0 Hz, 1 H, 14-H), 2.61 (br d,J=20.0 Hz, 1 H, 14-H), 2.49-2.40 (m, 1 H, 6-H), 2.16 (s, 3 H, Me), 2.08(s, 3 H, Me), 1.90-1.83 (m, 1 H, 6-H), 1.69 (s, 3 H, Me), 1.20 (s, 3 H,Me), 1.13 (s, 3 H, Me), 0.90 (t, J=8.0 Hz, 9 H, OSi(CH₂CH₃)₃), 0.56-0.49(band, 6 H, OSi(CH₂CH₃)₃); FAB HRMS (NBA/NaI) m/e 722.3354, M+Na⁺ calcdfor C₃₇H₅₃O₁₀NSi 722.3336.

Preparation of 1-naphthalene-C-2 ester derivative (Alcohol 19)

Alcohol 19. A solution of carbonate 7 (47 mg, 0.0812 mmol) intetrahydrofuran (2 mL) at −78° C. was treated with 1-lithionaphthalene(6.3 mL of a 0.32 M solution in diethylether, 2.03 mmol, prepared from1-bromonaphthalene from Aldrich Chemical Company Inc. and tButyllithium;methodology from Gilman, H.; Moore, F. W. J. Am. Chem. Soc. 1940, 62,1843) and stirred for 5 minutesutes. The reaction mixture was pouredinto a mixture of CH₂Cl₂ (15 mL) and aqueous NH₄Cl (20 mL), the organiclayer was separated, and the aqueous layer was extracted with CH₂Cl₂(2×10 mL). The combined organic layer was washed with brine (10 mL),dried (MgSO₄) and concentrated to give alcohol 19 which was taken intothe next step without further purification.

Physical Data for Alcohol 19. R_(f)=0.27 (20% ethylacetate in petroleumether); IR (film) v_(max) 3442, 2954, 2882, 1724, 1671, 1461, 1362,1279, 1228, 1195, 1092, 987, 826, 736 cm⁻¹; ¹H NMR (500 MHz, CDCl₃)δ8.66 (s, 1 H, naphthalene), 8.07 (dd, J=9.0, 2.0 Hz, 1 H, naphthalene),7.97-7.89 (m, 3 H, naphthalene), 7.68-7.57 (m, 2 H, naphthalene), 5.71(br d, J=6.5 Hz, 1 H, 2-H), 5.35 (d, J=2.5 Hz, 1 H, 10-H), 4.94 (br d,J=8.0 Hz, 1 H, 5-H), 4.41 (dd, J=11.0, 7.0 Hz, 1 H, 7-H), 4.37 (d, J=8.5Hz, 1 H, 20-H), 4.35 (d, J=2.0 Hz, 1 H, 10-OH), 4.18 (d, J=8.5 Hz, 1 H,20-H), 4.00 (d, J=6.5 Hz, 1 H, 3-H), 3.02 (d, J=19.5 Hz, 1 H, 14-H),2.69 (d, J=19.5 Hz, 1 H, 14-H), 2.54-2.45 (m, 1 H, 6-H), 2.27 (s, 3 H,Me), 2.13 (s, 3 H, Me), 1.94-1.87 (m, 1 H, 6-H), 1.86 (s, 1 H, OH), 1.75(s, 3 H, Me), 1.25 (s, 3 H, Me), 1.20 (s, 3 H, Me), 0.94 (t, J=8.0 Hz, 9H, OSi(CH₂Cl₃)₃), 0.63-0.49 (band, 6 H, OSi(CH₂CH₃)₃); FAB HRMS (NBA)m/e 707.3270, M+H⁺ calcd for C₃₉ H₅₀O₁₀Si 707.3252.

Preparation of phenylacetylide-C-2 ester derivative (Alcohol 20)

Alcohol 20. A solution of carbonate 7 (5.0 mg, 0.00864 mmol) intetrahydrofuran (0.5 mL) at −78° C. was treated with lithiumphenylacetylide from Aldrich Chemical Company Inc. (0.13 mL of a 1.0 Msolution in tetrahydrofuran, 0.13 mmol) and stirred for 0.5 hour Thereaction mixture was treated with aqueous NH₄Cl (0.5 mL), allowed towarm to 25° C., and diluted with H₂O (5 mL) and diethylether (5 mL). Theorganic layer was separated, dried, and concentrated to give a 9:1mixture of carbonate 7 and alcohol 20 (5.0 mg, 95%) as a film.

Physical Data for Alcohol 20. R_(f)=0.59 (50% ethylacetate in hexanes);¹H NMR (300 MHz, CDCl₃) δ7.63-7.57 (m, 2 H, Ar), 7.53-7.27 (m, 3 H, Ar),5.43 (d, J=6.5 Hz, 1 H, 2-H), 5.28 (d, J=2.5 Hz, 1 H, 10-H), 4.90 (br d,J=7.5 Hz, 1 H, 5-H), 4.67 (d, J=8.5 Hz, 1 H, 20-H), 4.44 (d, J=8.5 Hz, 1H, 20-H), 4.37-4.30 (m, 1 H, 7-H), 4.28 (d, J=2.5 Hz, 1 H, 10-OH), 3.88(d, J=6.5 Hz, 1 H, 3-H), 2.85 (d, J=20.2 Hz, 1 H, 14-H), 2.63 (d, J=20.2Hz, 1 H, 14-H), 2.55-2.47 (m, 1 H, 6-H), 2.11 (s, 3 H, OAc), 2.08 (s, 3H, 18-Me), 1.94-1.85 (m, 1 H, 6-H), 1.67 (s, 3 H, Me), 1.41 (s, 3 H,Me), 1.21 (s, 3 H, Me), 0.91 (t, J=8.0 Hz, 9 H, OSi(CH₂CH₃)₃),δ0.59-0.42 (band, 6 H, OSi(CH₂CH₃)₃).

Preparation of Hydroxycarbamate-C-2 ester derivative (Alcohol 21)

Alcohol 21. A solution of carbonate 7 (5.0 mg, 0.00864 mmol) in MeOH(0.5 mL) at 25° C. was treated with n-Butyl-NH₂ from Aldrich ChemicalCompany Inc. (0.05 mL, 0.506 nmmol) and stirred for 10 minutes. Thereaction mixture was concentrated and purified by flash chromatography(silica, 30→50% ethylacetate in petroleum ether) to give 21 (5.2 mg,92%) as an amorphous solid.

Physical Data for Alcohol 21. R_(f)=0.13 (silica, 30% ethylacetate inpetroleum ether); IR (film) v_(max) 3434, 2957, 2881, 1711, 1671, 1368,1243, 1108, 987, 829 cm⁻¹; ¹H NMR (500 MHz, CDCl₃) δ5.27 (d, J=2.0 Hz, 1H, 10-H), 5.23 (d, J=6.5 Hz, 1 H, 2-H), 4.91 (br d, J=8.0 Hz, 1 H, 5-H).4.79 (t, J=6.0 Hz, 1 H, NH), 4.47 (d, J=8.5 Hz, 1 H, 20-H), 4.34 (dd,J=11.0, 7.0 Hz, 1 H, 7-H), 4.30 (d, J=2.5 Hz, 1 H, 10-OH), 4.28 (d,J=8.5 Hz, 1 H, 20-H), 3.78 (d, J=6.5 Hz, 1 H, 3-H), 3.29-3.12 (m, 2 H,NHCH₂), 2.70 (d, J=20.0 Hz, IH, 14-H), 2.60 (d, J=20.0 Hz, 1 H, 14-H),2.51-2.42 (m, 1 H, 6-H), 2.24 (s, 1 H, OH), 2.06 (s, 3 H, Me), 2.05 (s,3 H, Me), 1.94-1.86 (m, 1 H, 6-H), 1.69 (s, 3 H, Me), 1.55-1.46 (m, 2 H,NHCH₂CH₂), 1.40-1.30 (m, 2 H, NHCH₂CH₂CH₂), 1.21 (s, 3 H, Me), 1.09 (s,3 H, Me), 0.95-0.80 (m, 12 H, CH₃ of Bu, OSi(CH₂CH₃)₃), 0.61-0.47 (band,6 H, OSi(CH₂CH₃)₃); FAB HRMS (NBA/NaI) m/e 674.3336, M+Na⁺ calcd forC₃₃H₅₃O₁₀NSi 674.3336.

Preparation of NN-methyl-phenyl-hydroxycarbamate-C-2 ester derivative(Alcohol 22)

Alcohol 22. A solution of carbonate 7 (5.0 mg, 0.00864 mmol) intetrahydrofuran (0.5 mL) at −78° C. was treated with LiNMePh (0.2 mL ofa 0.47 M solution in diethylether, 0.094 mmol, prepared fromN-methylaniline (Aldrich) and n-Butyllithium) and stirred for 1.25 hour.The reaction mixture was poured into a mixture of diethylether (5 mL)and aqueous NH₄Cl (5 mL), the organic layer was separated, and theaqueous layer was extracted with diethylether (2×5 mL). The combinedorganic layer was washed with brine (5 mL), dried (MgSO₄), concentrated,and purified by flash chromatography (silica, 15→35% ethylacetate inhexanes) to give 7 (2.5 mg, 50%) and 22 (2.8 mg, 93% based on 50%conversion) as an amorphous solid.

Physical Data for Alcohol 22. R_(f)=0.22 (silica 35% ethylacetate inpetroleum ether); ¹H NMR (500 MHz, CDCl₃) δ7.45-7.18 (band, 5 H), 5.25(br d, J=6.5 Hz, 1 H, 2-H), 5.20 (d, J=2.5 Hz, 1 H, 10-H), 4.70 (br d,J=8.0 Hz, 1 H, 5-H), 4.26 (d, J=2.5 Hz, 1 H, 10-OH), 4.22 (dd, J=10.5,6.5 Hz, 1 H, 7-H), 4.19 (d, J=8.5 Hz, 1 H, 20-H), 4.16 (d, J=8.5 Hz, 1H, 20-H), 3.58 (d, J=7.0 Hz, 1 H, 3-H), 3.27 (s, 3 H, MeN), 2.52 (d,J=20.0 Hz, 1 H, 14-H), 2.35 (d, J=20.0 Hz, 1 H, 14-H), 2.40-2.31 (m, 1H, 6-H), 2.03 (s, 1 H, OH), 1.97 (s, 3 H, Me), 1.85-1.76 (m, 1 H, 6-H),1.66 (s, 3 H, Me), 1.57 (s, 3 H, Me), 1.18 (s, 3 H, Me), 1.08 (s, 3 H,Me), 0.87 (t, J=8.0 Hz, 9 H, OSi(CH₂CH₃)₃), 0.55-0.43 (band, 6 H,OSi(CH₂CH₃)₃); FAB HRMS (NBA) m/e 686.3358, M+H⁺ calcd for C₃₆H₅₁O₁₀NSi686.3361.

Preparation of Thioether-C-2 ester derivative (Alcohol 23)

Alcohol 23. A solution of vinyl ester 9 (55.6 mg, 0.0916 mmol) and4-dimethylaminutesopyridine from Aldrich Chemical Company Inc. (DMAP,1.8 mg, 0.0147 mmol) in CH₂Cl₂ (4.3 mL) at 25° C. was treated with PhSHfrom Aldrich Chemical Company Inc. (0.030 mL, 0.292 mmol) and stirredfor 1.5 hour The reaction mixture was concentrated and purified by flashchromatography (silica, 30% ethylacetate in petroleum ether) to give 23(58.1, 88%) as a white solid.

Physical Data for Alcohol 23. R_(f)=0.37 (silica, 30% ethylacetate inhexanes), 0.34 (10% ethylacetate in PhH, 2 elutions); IR (film) v_(max)3441, 3057, 2956, 2883, 1732, 1672, 1600, 1367, 1238, 1111, 988, 825,739 cm⁻¹; ¹H NMR (500 MHz, CDC₁₃) δ7.39-7.24 (band, 5 H), 5.44 (d, J=6.5Hz, 1 H, 2-H), 5.28. (d, J=2.5 Hz, 1 H, 10-H), 4.90 (dd, J=9.5, 2.0 Hz,1 H, 5-H), 4.38 (d, J=8.0 Hz, 1 H, 20-H), 4.33 (dd, J=10.5, 6.5Hz, 1 H,7-H), 4.29 (d, J=2.5 Hz, 1 H, 10-OH), 4.18 (d, J=8.0 Hz, 1 H, 20-H),3.83 (d, J=6.5 Hz, 1 H, 3-H), 3.24-3.13 (m, 2 H, CH₂SPh), 2.76 (d,J=19.5 Hz, 1 H, 14-H), 2.72-2.58 (m, 3 H, 14-H, CH₂CH₂SPh), 2.47 (ddd,J=14.5, 9.5, 6.5 Hz, 1 H, 6-H), 2.39 (s, 1 H, OH), 2.07 (s, 3 H, Me),2.05 (s, 3 H, Me), 1.89 (ddd, J=14.5, 10.5, 2.0 Hz, 1 H, 6-H), 1.68 (s,3 H, Me), 1.23 (s, 3 H, Me), 1.12 (s, 3 H, Me), 0.92 (t, J=8.0 Hz, 9 H,OSi(CH₂CH₃)₃), 0.61-0.47 (band, 6 H, OSi(CH₂CH₃)₃); FAB HRMS (NBA/CsI)m/e 849.2085, M+Cs⁺ calcd for C₃₇H₅₂O₁₀SSi 849.2105.

Preparation of intermediates 25-27 and 2-furanyl-C-2-taxoid (28)

Acetate 25. A solution of alcohol 11 and 4-dimethylaminopyridine (DMAP,100 mg, 0.819 mnmol) in CH₂Cl₂ (3 mL) at 25° C. was treated with aceticanhydride (0.50 mL, 5.30 mmol) and stirred for 3 h. The reaction mixturewas diluted with CH₂Cl₂ (5 mL), treated with aqueous NaHCO₃ (7 mL), andstirred vigorously for 25 min. The organic layer was separated and theaqueous layer was extracted with CH₂Cl₂ (2×10 mL). The combined organiclayer was washed with brine (5 mL), dried (MgSO₄), concentrated, andpurified by preparative TLC (silica, 10% ethylacetate in benzene, 3elutions) to give 25 (36 mig, 66% from carbonate 7) as a white foarn.

Physical Data for Acetate 25. R_(f)=0.38 (20% ethylacetate in petroleumether); IR (film) v_(max) 3509, 2956, 2881, 1727, 1674, 1469, 1371,1299, 1227, 1108, 746 cm⁻¹; ¹H NMR (500 MHz, CDCl₃) δ7.65 (br s, 1 H,furan), 7.24 ( br d, J=3.0 Hz, 1 H, furan), 6.58-6.54 (m, 2 H, 10-H,furan), 5.59 (d, J=6.5 Hz, 1 H, 2-H), 4.92 (br d, J=7.5 Hz, 1 H, 5-H),4.46 (dd, J=10.5, 6.5 Hz, 1 H, 7-H), 4.42 (d, J=8.5 Hz, 1 H, 20-H), 4.16(d, J=8.5 Hz, 1 H, 20-H), 3.87 (d, J=6.5 Hz, 1 H, 3-H), 2.89 (d, J=20.0Hz, 1 H, 14-H), 2.63 (d, J=20.0 Hz, 1 H, 14-H), 2.59-2.48 (m, 1 H, 6-H),2.22 (s, 3 H, Me), 2.17 (s, 3 H, Me), 2.14 (s, 3 H, Me), 1.90-1.83 (m, 1H, 6-H), 1.65 (s, 3 H, Me), 1.25 (s, 3 H, Me), 1.18 (s, 3 H, Me), 0.91(t, J=8.0 Hz, 9 H, OSi(CH₂CH₃)₃), 0.64-0.52 (band, 6 H, OSi(CH₂CH₃)₃);FAB HRMS (NBA/CsI) m/e 821.1966, M+Cs⁺ calcd for C₃₅H₄₈O₁₂Si 821.1969.

Alcohol 26. A solution of enone 25 (36 mg, 0.0523 mmol) in MeOH (3 mL)containing two drops of CH₃COOH at 0° C. was treated with NaBH₄ (200 mg,5.29 mmol, added by portions) and stirred for 6 h. The reaction mixturewas diluted with CH₂C₁₂ (10 mL), treated with aqueous NH₄Cl (5 mL), andstirred for 10 min. The organic layer was separated and the aqueouslayer was extracted with CH₂Cl₂ (2×10 mL). The combined organic layerwas washed with brine (5 mL), dried (MgSO₄), concentrated, and purifiedby preparative TLC (silica, 50% ethylacetate in petroleum ether) to give26 (30 mg, 83% ) as an amorphous solid.

Physical Data for Alcohol 26. R_(f)=0.42 (silica, 50% ethylacetate inpetroleum ether); ¹H NMR (300 MHz, CDCl₃) δ7.62 (br s, 1 H, furan), 7.25(d, J=3.5 Hz, 1 H, furan), 6.58 (d, J=3.5 Hz, 1 H, furan), 6.43 (s, 1 H,10-H), 5.51 (d, J=7.0 Hz, 1 H, 2-H), 4.96 (d, J=7.5 Hz, 1 H, 5-H),4.85-4.79 (m, 1 H, 13-H), 4.48 (dd, J=10.5, 7.5 Hz, 1 H, 7-H), 4.38 (d,J=8.0 Hz, 1 H, 20-H), 4.15 (d, J=8.0 Hz, 1 H, 20-H), 3.82 (d, J=7.0 Hz,1 H, 3-H), 2.61-2.48 (m, 2 H, 6-H and 14-H), 2.28 (s, 3 H, OAc),2.20-2.10 (m, 1 H, 14-H), 2.18 (s, 6 H, OAc and 18-Me), 1.98-1.80 (m, 1H, 6-H), 1.18 (s, 3 H, 16-Me), 1.04 (s, 3 H, 17-Me), 0.90 (t, J=8.0 Hz,9 H, OSi(CH₂CH₃)₃), 0.65-0.50 (band, 6 H, OSi(CH₂CH₃)₃).

DiTES taxoid 27. To a solution of alcohol 26 (30.0 mg, 0.0434 mmol,previously azeotroped twice with benzene) and β-lactam 24 (28.0 mg,0.0734 mmol, previously azeotroped twice with benzene) in THF (2 mL),prepared from the Ojima-Holton protocol (Holton, R. A. Chem Abstr. 1990,114, 164568q; Ojima, I.; Habus, I.; Zhao, M.; Georg, G. I.; Jayasinghe,L. R. J. Org. Chem. 1991, 56, 1681-1683; Ojima, I.; Habus, I.; Zhao, M.;Zucco, M.; Park, Y. H.; Sun, C. M.; Brigaud, T. Tetrahedron 1992, 48,6985-7012), at 0° C. was added NaN(SiMe₃)₂ (0.130 mL of a 1.0 M solutionin THF, 0.130 mmol) dropwise. The resulting solution was stirred for 5min and poured into a mixture of CH₂Cl₂ (10 mL) and aqueous NH₄Cl (5mL). The organic layer was separated and the aqueous layer was extractedwith CH₂Cl₂ (2×5 mL). The combined organic layer was washed with brine(5 mL), dried (MgSO₄), concentrated, and purified by preparative TLC(silica, 60% ethylacetate in petroleum ether) to give 27 (12 mg, 26%) asan amorphous solid which was taken directly into the next step.

Taxoid 28. A solution of silyl ether 27 (6 mg, 0.00560 mmol) in THF (1mL) at 25° C. was treated with HF•pyridine (1 mL) and stirred for 1 h.The reaction mixture was poured into a mixture of ethylacetate (10 mL)and aqueous NaHCO₃ (10 mL) and the resulting mixture was stirred for 10min. The organic layer was separated and the aqueous layer was extractedwith ethylacetate (2×10 mL). The combined organic layer was washed withbrine (5 mL), dried (MgSO₄), concentrated, and purified by preparativeTLC (silica, 60% ethylacetate in petroleum ether) to give 28 (3 mg, 64%)as a colorless film.

Physical Data for Taxoid 28. R_(f)=0.1 (50% ethylacetate in petroleumether); IR (film) v_(max) 3383, 2933, 2898, 1729, 1649, 1519, 1242,1110, 1071 cm⁻¹; ¹H NMR (500 MHz, CDCl₃) δ7.77-7.73 (m, 2 H), 7.68-7.66(m, 1 H, furan), 7.55-7.33 (band, 9 H), 6.98 (d, J=30 9.0 Hz, 1 H, NH),6.58 (dd, J=3.5, 1.5 Hz, 1 H, furan), 6.27-6.21 (m, 2 H, 10-H, 13-H),5.80 (dd, J=9.0, 2.0 Hz, 1 H, 3′-H), 5.57 (d, J=7.0 Hz, 1 H, 2-H), 4.96(dd, J=10.0, 2.0 Hz, 1 H, 5-H), 4.80 (d, J=2.0 Hz, 1 H, 2′-H), 4.43-4.37(m, 2 H, 7-H, 20-H), 4.24 (d, J=8.5 Hz, 1 H, 20-H), 3.77 (d, J=7.0 Hz,1H, 3-H), 2.60-2.52 (m, 1 H, 6-H), 2.47 (d, J=4.0 Hz, 1 H, OH), 2.38 (s,3 H, Me), 2.35-2.21 (m, 2 H, 14-CH₂), 2.25 (s, 3 H, Me), 1.94-1.86 (m, 1H, 6-H), 1.81 (br s, 3 H, Me), 1.76 (s, 1 H, OH), 1.68 (s, 3 H, Me),1.25 (s, 3 H, Me), 1.13 (s, 3 H, Me).

Preparation of 2-thiophenyl-C-2 taxol (32)

Acetate 29. A solution of alcohol 12 (36.0 mg, 0.0543 mmol) and4-dimethylaminopyridine (DMAP, 33.0 mg, 0.270 mmol) in CH₂Cl₂ (3.0 mL)at 25° C. was treated with acetic anhydride (0.50 mL, 5.30 mmol) andstirred for 1 h. The reaction mixture was diluted with CH₂Cl₂ (10 mL),treated with aqueous NaHCO₃ (7 mL), and stirred vigorously for 0.5 h.The organic layer was separated and the aqueous layer was extracted withCH₂Cl₂ (2×10 mL). The combined organic layer was washed with brine (5mL), dried (MgSO₄), concentrated, and purified by flash chromatography(silica, 10→35% ethylacetate in hexanes) to give 29 (29.5 mg, 77%) as anamorphous solid.

Physical Data for Acetate 29. R_(f)=0.56 (silica, 50% ethylacetate inpetroleum ether); IR (film) v_(max) 3457, 2956, 1712, 1669, 1525, 1413,1376, 1264, 1227, 1073; ¹H NMR (500 MHz, CDCl₃) δ7.84 (dd, J=4.0, 1.5Hz, 1 H, thiophene), 7.63 (dd, J=5.0, 1.5 Hz, 1 H, thiophene), 7.13 (dd,J=5.0, 4.0 Hz, 1 H, thiophene), 6.56 (s, 1 H, 10-H), 5.58 (br d, J=6.5Hz, 1 H, 2-H), 4.90 (br d, J=8.0 Hz, 1 H, 5-H), 4.44 (dd, J=10.5, 7.0Hz, 1 H, 7-H), 4.42 (d, J=8.5 Hz, 1 H, 20-H), 4.18 (d, J=8.5 Hz, 1 H,20-H), 3.85 (d, J=6.5 Hz, 1 H, 3-H), 2.91 (d, J=19.5 Hz, 1 H, 14-H),2.64 (dd, J=19.5, 1.0 Hz, 1 H, 14-H), 2.55-2.48 (m, 1 H, 6-H), 2.20 (s,3 H, Me), 2.15 (s, 3 H, Me), 2.14 (s, 3 H, Me), 1.89-1.82 (m, 1 H, 6-H),1.65 (s, 3 H, Me), 1.23 (s, 3 H, Me), 1.16 (s, 3 H, Me), 0.88 (t, J=8.0Hz, 9 H, OSi(CH₂CH₃)₃), 0.59-0.53 (band, 6 H, OSi(CH₂CH₃)₃); FAB HRMS(NBA/CsI) m/e 837.1736, M+Cs⁺ calcd for C₃₅H₄₈O₁₁SSi 837.1741.

Alcohol 30. A solution of enone 29 (29.0 mg, 0.0411 mmol) in MeOH (5 mL)at 0° C. was treated with NaBH₄ (30.2 mg, 0.80 mmol, added by portions)and stirred for 2.5 h. The reaction mixture was diluted with CH₂Cl₂ (15mL), treated with aqueous NH₄Cl (5 mL), and stirred for 10 min. Theorganic layer was separated and the aqueous layer was extracted withCH₂Cl₂ (2×10 mL). The combined organic layer was washed with brine (5mL), dried (MgSO₄), concentrated, and purified by flash chromatography(silica, 25→50% ethylacetate in petroleum ether) to give 29 (4.0 mg,14%) and 30 (14.7 mg, 59% based on 86% conversion) as an amorphoussolid.

Physical Data for Alcohol 30. R_(f)=0.34 (silica, 50% ethylacetate inpetroleum ether); IR (film) v_(max) 3478, 2946, 2892, 1717, 1520, 1365,1238, 1083; ¹H NMR (500 MHz, CDCl₃) δ7.85 (dd, J=3.5, 1.5 Hz, 1 H,thiophene), 7.61 (dd, J=5.0, 1.5 Hz, 1 H, thiophene), 7.12 (dd, J=5.0,3.5 Hz, 1 H, thiophene), 6.43 (s, 1 H, 10-H), 5.51 (d, J=7.0 Hz, 1 H,2-H), 4.94 (br d, J=7.5 Hz, 1 H, 5-H), 4.83-4.77 (m, 1 H, 13-H), 4.45(dd, J=10.5, 7.5 Hz, 1 H, 7-H), 4.41 (d, J=8.0 Hz, 1 H, 20-H), 4.19 (brd, J=8.0 Hz, 1 H, 20-H), 3.82 (d, J=7.0 Hz, 1 H, 3-H), 2.55-2.48 (m, 1H, 6-H), 2.24 (s, 3 H, Me), 2.26-2.21 (m, 2 H, 14-CH₂), 2.16 (d, J=1.0Hz, 3 H, 18-Me), 2.15 (s, 3 H, Me), 2.00 (d, J=5.0 Hz, 1 H, OH),1.90-1.82 (m, 1 H, 6-H), 1.66 (s, 3 H, Me), 1.58 (s, 1 H, OH), 1.15 (s,3 H, Me), 1.02 (s, 3 H, Me), 0.90 (t, J=8.0 Hz, 9 H, OSiCH₂CH₃)₃),0.59-0.55 (band, 6 H, OSi(CH₂CH₃)₃); FAB HRMS (NBA/CsI) m/e 839.1893,M+Cs⁺ calcd for C₃₅H₅₀O₁₁SSi 839.1897.

DITES taxoid 31. To a solution of alcohol 30 (14.5 mg, 0.0205 mmol,previously azeotroped twice with benzene) and β-lactam 24 (16.0 mg,0.0420 mmol, previously azeotroped twice with benzene) in THF (1.0 mL),prepared from the Ojima-Holton protocol (Holton, R. A. Chem Abstr. 1990,114, 164568q; Ojima, I.; Habus, I.; Zhao, M.; Georg, G. I.; Jayasinghe,L. R. J. Org. Chem. 1991, 56, 1681-1683; Ojima, I.; Habus, I.; Zhao, M.;Zucco, M.; Park, Y. H.; Sun, C. M.; Brigaud, T. Tetrahedron 1992, 48,6985-7012), at −78° C. was added NaN(SiMe₃)₂ (0.051 mnL of a 1.0 Msolution in THF, 0.051 mmol) dropwise. The resulting solution wasstirred for 0.5 h and poured into a mixture of diethylether (10 mL) andaqueous NH₄Cl (5 mL). The organic layer was separated and the aqueouslayer was extracted with diethylether (2×5 mL). The combined organiclayer was washed with brine (5 mL), dried (MgSO₄), concentrated, andpurified by flash chromatography (silica, 10→35% ethylacetate inhexanes) followed by preparative TLC (silica, 15% ethylacetate inbenzene) to give 30 (3.0 mg, 21%) and 31 (7.6 mg, 43% based on 79%conversion) as a white solid.

Physical Data for DITES taxoid 31. R_(f)=0.48 (silica, 50% ethylacetatein hexanes); IR (film) v_(max) 3382, 2913, 2850, 1722, 1653, 1461, 1243,1083, 1014; ¹H NMR (500 MHz, CDCl₃) δ7.90 (br d, J=4.0 Hz, 1 H,thiophene), 7.74 (d, J=8.0 Hz, 2 H, NBz), 7.62 (br d, J=5.0 Hz, 1 H,thiophene), 7.48 (t, J=7.0 Hz, 1 H, Ar), 7.42-7.28 (band, 7 H, Ar), 7.14(dd, J=5.0, 4.0 Hz, 1 H, thiophene), 7.10 (d, J=9.0 Hz, 1 H, NH), 6.42(s, 1 H, 10-H), 6.20 (br t, J=9.0 Hz, 1 H, 13-H), 5.65 (br d, J=9.0 Hz,1 H, 3′-H), 5.57 (d, J=7.0 Hz, 1 H, 2-H), 4.94 (br d, J=8.5 Hz, 1 H,5-H), 4.67 (d, J=1.5 Hz, 1 H, 2′-H), 4.44 (dd, J=11.0, 6.5 Hz, 1 H,7-H), 4.43 (d, J=8.5 Hz, 1 H, 20-H), 4.26 (d, J=8.5 Hz, 1 H, 20-H), 3.77(d, J=7.0 Hz, 1 H, 3-H), 2.51 (s, 3 H, Me), 2.54-2.47 (m, 1 H, 6-H),2.34 (dd, J=15.0, 9.5 Hz, 1 H, 14-H), 2.15 (s, 3 H, Me), 2.10 (dd,J=15.0, 9.0, 1 H, 14-H), 1.99 (s, 3 H, Me), 1.93-1.86 (m, 1 H, 6-H),1.72 (s, 1 H, OH), 1.68 (s, 3 H, Me), 1.18 (s, 3 H, Me), 1.16 (s, 3 H,Me), 0.90 (t, J=8.0 Hz, 9 H, Si(CH₂Cl₃)₃), 0.79 (t, J=8.0 Hz, 9 H,Si(CH₂CH₃)₃), 0.57-0.55 (band, 6 H, Si(CH₂CH₃)₃), 0.45-0.40 (band, 6 H,Si(CH₂CH₃)₃); FAB HRMS (NBA/CsI) m/e 1220.3685 M+Cs⁺ calcd forC₅₇H₇₇O₁₄NSSi₂ 1220.3658.

Taxoid 32. A solution of silyl ether 31 (7.5 mg, 0.00689 mmol) in THF(0.8 mL) at 25° C. was treated with HF•pyridine (0.150 mL) and stirredfor 1 h. The reaction mixture was poured into a mixture of ethylacetate(10 mL) and aqueous NaHCO₃ (5 mL) and the resulting mixture was stirredfor 10 min. The organic layer was separated and the aqueous layer wasextracted with ethylacetate (2×10 mL). The combined organic layer waswashed with brine (5 mL), dried (MgSO₄), concentrated, and purified byflash chromatography (silica, 50→100% ethylacetate in petroleum ether)to give 32 (4.2 mg, 71%) as a colorless film.

Physical Data for Taxoid 32. R_(f)=0.44 (silica, 75% ethylacetate inpetroleum ether); IR (film) v_(max) 3417, 2929, 1716, 1649, 1521, 1460,1417, 1368, 1247, 1076; ¹H NMR (500 MHz, CDCl₃) δ7.90 (dd, J=4.0, 1.0Hz, 1 H, thiophene), 7.73 (d, J=7.0 Hz, 2 H, NBz), 7.63 (dd, J=5.0, 1.0Hz, 1 H, thiophene), 7.51-7.32 (band, 8 H, Ar), 7.14 (dd, J=5.0, 4.0 Hz,1 H, thiophene), 6.96 (d, J=9.0 Hz, 1 H, NH), 6.24 (s, 1 H, 10-H), 6.19(br t, J=9.0 Hz, 1 H, 13-H), 5.75 (dd, J=9.0, 2.5 Hz, 1 H, 3′-H), 5.55(d, J=7.0 Hz, 1 H, 2-H), 4.94 (br d, J=8.0 Hz, 1 H, 5-H), 4.76 (dd,J=5.0, 2.5 Hz, 1 H, 2′-H), 4.41 (d, J=8.5 Hz, 1 H, 20-H), 4.40-4.33 (m,1 H, 7-H), 4.24 (d, J=8.5 Hz, 1 H, 20-H), 3.73 (d, J=7.0 Hz, 1 H, 3-H),3.52 (d, J=5.0 Hz, 1 H, 2′-OH), 2.58-2.49 (m, 1 H, 6-H), 2.44 (d, J=4.0Hz, 1 H, 7-OH), 2.35 (s, 3 H, Me), 2.29 (d, J=9.0 Hz, 2 H, 14-CH₂), 2.22(s, 3 H, Me), 1.91-1.83 (m, 1 H, 6-H), 1.76 (s, 3 H, Me), 1.66 (s, 3 H,Me), 1.23 (s, 3 H, Me), 1.10 (s, 3 H, Me); FAB HRMS (NBA/CsI) m/e992.1252, M+Cs⁺ calcd for C₄₅H₄₉NO₁₄S 992.1928.

Preparation of 3-thiophenyl-C-2 taxol (36)

Acetate 33. A solution of alcohol 13 (68.4 mg, 0.103 mmol) and4-dimethylaminopyridine (DMAP, 37.8 mg, 0.309 mmol) in CH₂Cl₂ (4.4 mL)at 25° C. was treated with acetic anhydride (0.370 mL, 3.92 mmol) andstirred for 2 h. The reaction mixture was diluted with CH₂Cl₂ (5 mL),treated with aqueous NaHCO₃ (7 mL), and stirred vigorously for 25 min.The organic layer was separated and the aqueous layer was extracted withCH₂Cl₂ (2×10 mL). The combined organic layer was washed with brine (5mL), dried (MgSO₄), concentrated, and purified by flash chromatography(silica, 30% ethylacetate in hexanes) to give 33 (66.0 mg, 91%) as anamorphous solid.

Physical Data for Acetate 33. R_(f)=0.48 (silica, 10% ethylacetate inbenzene, 3 elutions); IR (film) v_(max) 3518, 2956, 2881, 1727, 1676,1520, 1460, 1371, 1236, 1098, 985, 824, 744 cm⁻¹; ¹H NMR (500 MHz,CDCl₃) δ8.19 (dd, J=3.0, 1.1 Hz, 1 H, thiophene), 7.55 (dd, J=5.0, 1.1Hz, 1 H, thiophene), 7.38 (dd, J=5.0, 3.0 Hz, 1 H, thiophene), 6.58 (s,1 H, 10-H), 5.61 (dd, J=6.5, 0.7 Hz, 1 H, 2-H), 4.92 (dd, J=9.5, 2.0 Hz,1 H, 5-H), 4.47 (dd, J=10.5, 6.5 Hz, 1 H, 7-H), 4.38 (d, J=8.5 Hz, 1 H,20-H), 4.14 (d, J=8.5 Hz, 1 H, 20-H), 3.88 (d, J=6.5 Hz, 1 H, 3-H), 2.89(d, J=20 Hz, 1 H, 14-H), 2.64 (br d, J=20 Hz, 1 H, 14-H), 2.54 (ddd,J=14.5, 9.5, 6.5 Hz, 1 H, 6-H), 2.23 (s, 3 H, Me), 2.18 (s, 3 H, Me),2.17 (s, 3 H, Me), 1.87 (ddd, J=14.5, 10.5, 2.0, 1 H, 6-H), 1.85 (s, 1H, OH), 1.66 (s, 3 H, Me), 1.26 (s, 3 H, Me), 1.19 (s, 3 H, Me), 0.92(t, J=8.0 Hz, 9 H, OSi(CH₂CH₃)₃), 0.65-0.54 (band, 6 H, OSi(CH₂CH₃)₃);FAB HRMS (NBA/CsI) m/e 837.1760, M+Cs⁺ calcd for C₃₅H₄₈O₁₁SSi 837.1741.

Alcohol 34. A solution of enone 33 (57.3 mg, 0.0813 mmol) in MeOH-THF(5:1, 4.1 mL) at 0° C. was treated with NaBH₄ (69.1 mg, 1.83 mmol, addedby portions) and stirred for 2.5 h. The reaction mixture was dilutedwith CH₂CI₂ (10 mL), treated with aqueous NH₄Cl (5 mL), and stirred for10 min. The organic layer was separated and the aqueous layer wasextracted with CH₂Cl₂ (2×10 mL). The combined organic layer was washedwith brine (5 mL), dried (MgSO₄), concentrated, and purified by flashchromatography (silica, 30% ethylacetate in hexanes) to give 33 (6.8 mg,12%) and 34 (45.2 mg, 89% based on 88% conversion) as an amorphoussolid.

Physical Data for Alcohol 34. R_(f)=0.48 (silica, 50% ethylacetate inhexanes); IR (film) v_(max) 3520, 2953, 2881, 1719, 1520, 1370, 1238,1100, 979, 823, 746 cm⁻¹; ¹H NMR (500 MHz, CDCl₃) δ8.20 (dd, J=3.0, 1.0Hz, 1 H, tbiophene), 7.57 (dd, J=5.0, 1.0 Hz, 1 H, thiophene), 7.35 (dd,J=5.0, 3.0 Hz, 1 H, thiophene), 6.45 (s, 1 H, 10-H), 5.54 (d, J=7.0 Hz,1 H, 2-H), 4.96 (br d, J=8.5 Hz, 1 H, 5-25 H), 4.82 (br dd, J=12.0, 8.0Hz, 1 H, 13-H), 4.48 (dd, J=10.5, 6.5 Hz, 1 H, 7-H), 4.36 (d, J=8.5 Hz,1 H, 20-H), 4.15 (d, J=8.5 Hz, 1 H, 20-H), 3.85 (d, J=7.0 Hz, 1 H, 3-H),2.53 (ddd, J=14.5, 9.5, 6.5, 1 H, 6-H), 2.27 (s, 3 H, Me), 2.28-2.21 (m,2 H, 14-CH₂), 2.18 (s, 6 H, Me, Me), 2.03 (s, 1 H, OH), 1.87 (ddd,J=14.5, 10.5, 2.0 Hz, 1 H, 6-H), 1.67 (s, 3 H, Me), 1.65 (s, 1 H, OH),1.18 (s, 3 H, Me), 1.04 (s, 3 H, Me), 0.92 (t, J=8.0 Hz, 9 H,OSi(CH₂CH₃)₃), 0.64-0.50 (band, 6 H, OSi(CH₂CH₃)₃); FAB HRMS (NBA/CsI)m/e 839.1908 M+Cs⁺ calcd for C₃₅H₅₀O₁₁SSi 839.1897.

DiTES taxoid 35. To a solution of alcohol 34 (19.5 mg, 0.0276 mmol,previously azeotroped twice with benzene) and β-lactam 24 (27.5 mg,0.0721 mmol, previously azeotroped twice with benzene) in THF (1.4 mL),prepared from the Ojima-Holton protocol (Holton, R. A. Chem Abstr.1990,114, 164568q; Ojima, I.; Habus, I.; Zhao, M.; Georg, G. I.;Jayasinghe, L. R. J. Org. Chem. 1991, 56, 1681-1683; Ojima, I.; Habus,I.; Zhao, M.; Zucco, M.; Park, Y. H.; Sun, C. M.; Brigaud, T.Tetrahedron 1992, 48, 6985-7012), at 0° C. was added NaN(SiMe₃)₂ (0.066mL of a 1.0 M solution in THF, 0.066 mmol) dropwise. The resultingsolution was stirred for 0.5 h and poured into a mixture of CH₂Cl₂ (10mL) and aqueous NH₄Cl (5 mL). The organic layer was separated and theaqueous layer was extracted with CH₂CI₂ (2×5 mL). The combined organiclayer was washed with brine (5 mL), dried (MgSO₄), concentrated, andpurified by flash chromatography (silica, 20→30 % ethylacetate inhexanes) to give 34 (1.1 mg, 6%) and 35 (17.3 mg, 61% based on 94%conversion) as a white solid.

Physical Data for DiTES taxoid 35. R_(f)=0.86 (silica, 50% ethylacetatein hexanes); IR (film) v_(max) 3519, 3437, 2953, 2879, 1726, 1666, 1515,1483, 1369, 1240, 1100, 979, 825, 746 cm⁻¹; ¹H NMR (500 MHz, CDCl₃)δ8.32 (dd, J=3.0, 1.2 Hz, 1 H, thiophene), 7.76-7.73 (m, 2 H), 7.60 (dd,J=5.0, 1.2 Hz, 1 H, thiophene), 7.52-7.29 (band, 9 H), 7.10 (d, J=9.0Hz, 1 H, NH), 6.44 (s, 1 H, 10-H), 6.26 (br t, J=9.0 Hz, 1 H, 13-H),5.72 (dd, J=9.0, 2.0 Hz, 1 H, 3′-H), 5.61 (d, J=7.0 Hz, 1 H, 2-H), 4.95(dd, J=9.5, 2.0 Hz, 1 H, 5-H), 4.70 (d, J=2.0 Hz, 1 H, 2′-H), 4.48 (dd,J=10.5, 6.5 Hz, 1 H, 7-H), 4.37 (d, J=8.5 Hz, 1 H, 20-H), 4.23 (d, J=8.5Hz, 1 H, 20-H), 3.81 (d, J=7.0 Hz, 1 H, 3-H), 2.56-2.49 (m, 1 H, 6-H),2.54 (s, 3 H, Me), 2.35 (dd, J=15.5, 9.0 Hz, 1 H, 14-H), 2.17 (s, 3 H,Me), 2.07 (dd, J=15.5, 9.0 Hz, 1 H, 14-H), 2.03 (d, J=1.0 Hz, 3 H,18-Me), 1.94-1.87 (m, 1 H, 6-H), 1.69 (s, 3 H, Me), 1.68 (s, 1 H, OH),1.20 (s, 3 H, Me), 1.18 (s, 3 H, Me), 0.93 (t, J=8.0 Hz, 9 H,OSi(CH₂CH₃)₃), 0.81 (t, J=8.0 Hz, 9 H, OSi(CH₂CH3)₃), 0.63-0.53 (band, 6H, OSi(CH₂CH₃)₃), 0.52-0.36 (band, 6 H, OSi(CH₂CH₃)₃); FAB HRMS(NBA/CsI) m/e 1220.3675, M+Cs⁺ calcd for C₅₇H₇₇O₁₄SSi₂N 1220.3658.

Taxoid 36. A solution of silyl ether 35 (17.3 mg, 0.0159 mmol) in THF(0.6 mL) at 25° C. was treated with HF-pyridine (0.150 mL) and stirredfor 2 h. The reaction mixture was poured into a mixture of ethylacetate(10 mL) and aqueous NaHCO₃ (5 mL) and the resulting mixture was stirredfor 10 min. The organic layer was separated and the aqueous layer wasextracted with ethylacetate (2×10 mL). The combined organic layer waswashed with brine (5 mL), dried (MgSO₄), concentrated, and purified bypreparative TLC (silica, 25% ethylacetate in petroleum ether) to give 36(7.7 mg, 56%) as a colorless film.

Preparation of Taxoid 36. R_(f)=0.11 (silica, 50% ethylacetate inhexanes); IR (film) v_(max) 3496, 3434, 2940, 1723, 1648, 1519, 1370,1243, 1071, 975 cm⁻¹; ¹H NMR (500 MHz, CDCl₃) δ8.32 (dd, J=3.0, 1.0 Hz,1 H, thiophene), 7.75-7.72 (m, 2 H), 7.60 (dd, J=5.0, 1.0 Hz, 1 H,thiophene), 7.53-7.33 (band, 9 H), 6.95 (d, J=9.0 Hz, 1 H, NH),6.28-6.23 (m, 2 H, 10-H, 13-H), 5.81 (dd, J=9.0, 2.0 Hz, 1 H, 3′-H),5.58 (d, J=7.0 Hz, 1 H, 2-H), 4.95 (dd, J=9.5, 2.0 Hz, 1 H, 5-H), 4.80(dd, J=4.5, 2.0 Hz, 1 H, 2′-H), 4.41 (br t, J=7.5 Hz, 1 H, 7-H), 4.36(d, J=8.5 Hz, 1 H, 20-H), 4.22 (d, J=8.5 Hz, 1 H, 20-H), 3.78 (d, J=7.0Hz, 1 H, 3-H), 3.49 (d, J=4.5 Hz, 1 H, 2′-OH), 2.55 (ddd, J=14.5, 9.5,6.5 Hz, 1 H, 6-H), 2.45 (br s, 1 H, OH), 2.40 (s, 3 H, Me), 2.34 (dd,J=15.5, 9.0 Hz, 1 H, 14-H), 2.25 (dd, J=15.5, 9.0 Hz, 1 H, 14-H), 2.24(s, 3 H, Me), 1.89 (ddd, J=14.5, 11.0, 2.0 Hz, 1 H, 6-H), 1.81 (d, J=2.0Hz, 3 H, 18-Me), 1.74 (br s, 1 H, OH), 1.67 (s, 3 H, Me), 1.24 (s, 3 H,Me), 1.13 (s, 3 H, Me); FAB HRMS (NBA/CsI) m/e 992.1940, M+Cs⁺ calcd forC₄₅H₄₉O₁₄NS 992.1928.

Preparation of 2-pyridinyl-C-2 taxol (40)

Acetate 37. A solutionl of alcohol 15. (23.2 mg, 0.0353 mnmol) and4-dimethylaminopyridine (DMAP, 12.9 mg, 0.106 mnmol) in CH₂Cl₂ (1.5 mL)at 25° C. was treated with acetic anhydride (0.126 mL, 1.34 mmnol) andstirred for 2 h. The reaction mixture was diluted with ethylacetate (5mL), treated with aqueous NaHCO₃ (7 mL), and stirred vigorously for 25min. The organic layer was separated and the aqueous layer was extractedwith ethylacetate (2×10 mL). The combined organic layer was washed withbrine (5 mL), dried (MgSO₄), concentrated, and purified by flashchromatography (silica, 70→100% ethylacetate in petroleum ether) to give37 (19.0 mg, 77%) as an amorphous solid.

Preparation of Acetate 37. R_(f)=0.58 (silica, ethylacetate); IR (film)V_(max) 3482, 2954, 2881, 1730, 1675, 1370, 1304, 1231, 1118, 987, 823,739 cm⁻¹; ¹H NMR (500 MHz, CDCl₃) δ8.77 (ddd, J=4.5, 1.7, 1.0 Hz, 1 H,pyridine), 8.05 (ddd, J=8.0, 1.0, 1.0 Hz, 1 H. pyridine), 7.89 (ddd,J=8.0, 8.0, 1.7 Hz, 1 H, pyridine), 7.53 (ddd, J=8.0, 4.5, 1.0 Hz, 1 H,pyridine), 6.59 (s, 1 H, 10-H), 5.65 (dd, J=6.6, 1.0 Hz, 1 H, 2-H), 4.92(dd, J 9.5, 2.0 Hz, 1 H, 5-H), 4.48 (dd, J=10.5, 7.0 Hz, 1 H, 7-H), 4.35(d, J=8.5 Hz, 1 H, 20-H), 4.26 (dd, J=8.5, 1.0 Hz, 1 H, 20-H), 3.91 (d,J=6.5 Hz, 1 H, 3-H), 3.00 (d, J=20.0 Hz, 1 H, 14-H), 2.71 (dd, J=20.0,1.0 Hz, 1 H, 14-H), 2.54 (ddd, J=14.5, 9.5, 7.0 Hz, 1 H, 6-H), 2.53 (s,1 H, OH), 2.23 (s, 3 H, Me), 2.18 (s, 3 H, Me), 2.14 (s, 3 H, Me), 1.88(ddd, J=14.5, 10.5, 2.0 Hz, 1 H, 6-H), 1.70 (s, 3 H, Me), 1.27 (s, 3 H,Me), 1.20 (s, 3 H, Me), 0.92 (t, 9 H, J=8.0 Hz, OSi(CH₂CH₃)₃), 0.64-0.52(band, 6 H, OSi(CH₂CH₃)₃); FAB HRMS (NBA/CsI) m/e 832.2139, M+Cs⁺ calcdfor C₃₆ H₄₉O₁₁NSi 832.2129.

Alcohol 38. A solution of enone 37 (47.6 mg, 0.0680 mmol) in MeOH-THF (51, 3.8 mL) at 0° C. was treated with NaBH₄ (46.0 mg, 1.22 mmol, added byportions) and stirred for 1.5 h. The reaction mixture was diluted withethylacetate (10 mL), treated with aqueous NH₄Cl (5 mL), and stirred for10 min. The organic layer was separated and the aqueous layer wasextracted with ethylacetate (2×10 mL). The combined organic layer waswashed with brine (5 mL), dried (MgSO₄), concentrated, and purified byflash chromatography (basic alumina, ethylacetate →10% MeOH inethylacetate) to give 27f (28.0 mg, 59%) as an amorphous solid.

Physical Data for Alcohol 38. R_(f)=0.36 (silica, ethylacetate); IR(film) v_(max) 3487, 2951, 2880, 1736, 1583, 1369, 1307, 1236, 1132,983, 824, 739 cm⁻¹; ¹H NMR (500 MHz, CDCl₃) δ8.79 (dm, J=4.5 Hz, 1 H,pyridine), 8.13 (br d, J=7.5 Hz, 1 H, pyridine), 7.88 (ddd, J=7.5, 7.5,1.7 Hz, 1 H, pyridine), 7.51 (ddd, J=7.5, 4.5, 1.0 Hz, 1 H, pyridine),6.46 (s, 1 H, 10-H), 5.64 (d, J=7.0 Hz, 1 H, 2-H), 4.96 (dd, J=9.5, 2.0Hz, 1 H, 5-H), 4.85 (br t, J=8.0 Hz, 1 H, 13-H), 4.49 (dd, J=10.5, 6.5Hz, 1 H, 7-H), 4.31 (d, J=8.0 Hz, IH, 20-H), 4.25 (d, J=8.0 Hz, 1 H,20-H), 3.89 (d, J=7.0 Hz, 1 H, 3-H), 2.53 (ddd, J=14.5, 9.5, 6.5 Hz, 1H, 6-H), 2.36-2.11 (m, 2 H, 14-CH₂), 2.25 (s, 3 H, Me), 2.19 (d, J=1.0Hz, 3 H, 18-Me), 2.18 (s, 3 H, Me), 1.88 (ddd, J=14.0, 10.5, 2.5 Hz, 1H, 6-H), 1.70 (s, 3 H, Me), 1.20 (s, 3 H, Me), 1.05 (s, 3 H, Me), 0.92(t, J=8.0 Hz, 9 H, OSi(CH₂CH₃)₃), 0.65-0.51 (band, 6 H, OSi(CH₂CH₃)₃);FAB HRMS (NBA/CsI) m/e 834.2311, M+Cs⁺ calcd for C₃₆ H₅₁O₁₁NSi 834.2286.

DiTES taxoid 39. To a solution of alcohol 38 (10.3 mg, 0.0147 mmol,previously azeotroped twice with benzene) and β-lactam 24 (17.0 mg,0.0446 mmol, previously azeotroped twice with benzene) in THF (0.75 mL)at 0° C., prepared from the Ojima-Holton protocol (Holton, R. A. ChemAbstr. 1990, 114, 164568q; Ojima, I.; Habus, I.; Zhao, M,; Georg, G. I.;Jayasinghe, L. R. J. Org. Chem. 1991, 56, 1681-1683; Ojima, I.; Habus,I.; Zhao, M.; Zucco, M.; Park, Y. H.; Sun, C. M.; Brigaud, T.Tetrahedron 1992, 48, 6985-7012), was added NaN(SiMe₃)₂ (0.038 mL of a1.0 M solution in THF, 0.038 mmol) dropwise. The resulting solution wasstirred for 20 min and poured into a mixture of ethylacetate (10 mL) andaqueous NH₄Cl (5 mL). The organic layer was separated and the aqueouslayer was extracted with ethylacetate (2×5 mL). The combined organiclayer was washed with brine (5 mL), dried (MgSO₄), concentrated, andpurified by preparative TLC (silica, 60% ethylacetate in petroleumether) to give 39 (2.7 mg, 17%) as a film.

Physical Data for DiTES taxoid 39. R_(f)=0.28 (silica, 50% ethylacetatein hexane); IR (film) v_(max) 3429, 2952, 2927, 2878, 1728, 1662, 1585,1369, 1236, 1124, 1016, 984, 742 cm⁻¹; ¹H NMR (500 MHz, CDCl₃) δ8.78 (brd, J=4.5 Hz, 1 H, pyridine), 8.21 (d, J=8.0 Hz, 1 H, pyridine), 7.95(ddd, J=8.0, 8.0, 1.7 Hz, 1 H, pyridine), 7.75-7.70 (m, 2 H), 7.54-7.22(band, 9 H), 7.12 (d, J=9.0 Hz, 1 H, NH), 6.45 (s, 1 H, 10-H), 6.27 (brt, J=9.0 Hz, 1 H, 13-H), 5.73-5.67 (m, 2 H, 2-H, 3′-H), 4.95 (dd, J=9.5,2.0 Hz, 1 H, 5-H), 4.70 (d, J=2.0 Hz, 1 H, 2′-H), 4.48 (dd, J=10.5, 6.5,1 H, 7-H), 4.32 (br s, 2 H, 20-CH₂), 3.85 (d, J=7.0 Hz, 1 H, 3-H),2.56-2.48 (m, 1 H, 6-H), 2.52 (s, 3 H, Me), 2.40 (dd, J=15.0 Hz, 9.5 Hz,1 H, 14-H), 2.20-2.12 (m, 2 H, 14-H, OH), 2.18 (s, 3 H, Me), 2.04 (s, 3H, Me), 1.92 (ddd, J=14.5, 10.5, 2.0 Hz, 1 H, 6-H), 1.72 (s, 3 H, Me),1.22 (s, 3 H, Me), 1.19 (s, 3 H, Me), 0.93 (t, J=8.0 Hz, 9 H,OSi(CH₂CH₃)₃), 0.81 (t, J=8.0 Hz, 9 H, OSi(CH₂CH₃)₃), 0.64-0.34 (band,12 H, OSi(CH₂CH₃)₃); FAB HRMS (NBA/CsI) m/e 1215.4065, M+Cs⁺ calcd forC₅₈H₇₈O₁₄N₂Si₂ 1215.4046.

Taxoid 40. A solution of silyl ether 39 (2.7 mg, 0.00249 mmol) in THF(0.4 mL) at 25° C. was treated with HF•pyridine (0.170 mL) and stirredfor 3 h. The reaction mixture was poured into a mixture of ethylacetate(10 mL) and aqueous NaHCO₃ (5 mL) and the resulting mixture was stirredfor 10 min. The organic layer was separated and the aqueous layer wasextracted with ethylacetate (2×10 mL). The combined organic layer waswashed with brine (5 mL), dried (MgSO₄), concentrated, and purified bypreparative TLC (silica, ethylacetate) to give 40 (0.8 mg, 38%) as acolorless film.

Physical Data for Taxoid 40. R_(f)=0.54 (silica, ethylacetate); ¹H NMR(500 MHz, CDCl₃) δ8.80 (br d, J=4.5 Hz, 1 H, pyridine), 8.22 (d, J=7.5Hz, 1 H, pyridine), 7.93 (ddd, J=7.5, 7.5, 1.5 Hz, 1 H, pyridine),7.75-7.71 (m, 2 H), 7.54-7.30 (band, 9 H), 6.98 (d, J=9.0 Hz, 1 H, NH),6.30-6.24 (m, 2 H, 10-H, 13-H), 5.82 (dd, J=9.0, 2.5 Hz, 1 H, 3′-H),5.67 (d, J=7.0 Hz, 1 H, 2-H), 4.95 (dd, J=10.0, 2.0 Hz, 1 H, 5-H), 4.81(dd, J=4.5, 2.5 Hz, 1 H, 2′-H), 4.41 (ddd, J=11.0, 7.0, 4.5 Hz, 1 H,7-H), 4.31 (s, 2 H, 20-CH₂), 3.81 (d, J=7.0 Hz, 1 H, 3-H), 3.52 (br s, 1H, OH), 3.50 (d, J=4.5 Hz, 1 H, 2′-OH), 2.56 (ddd, J=14.5, 9.5, 7.0 Hz,1 H, 6-H), 2.46 (d, J=4.0 Hz, 1 H, 7-OH), 2.43-2.30 (m, 2 H, 14-CH₂),2.38 (s, 3 H, OAc), 2.25 (s, 3 H, OAc), 1.90 (ddd, J=14.5, 11.0, 2.0 Hz,1 H, 6-H), 1.81 (s, 3 H, Me), 1.71 (s, 3 H, Me), 1.26 (s, 3 H, Me), 1.15(s, 3 H, Me).

Prepartion of 3-pyridinyl-C-2-taxol (44)

Acetate 41. A solution of alcohol 17 (42.9 mg, 0.0652 mmol) and4-dimethylaminopyridine (DMAP, 23.9 mg, 0.196 nmmol) in CH₂Cl₂ (2.8 mL)at 25° C. was treated with acetic anhydride (0.235 mL, 2.49 mmol) andstirred for 2 h. The reaction mixture was diluted with ethylacetate (5mL), treated with aqueous NaHCO₃ (7 mL), and stirred vigorously for 25min. The organic layer was separated and the aqueous layer was extractedwith ethylacetate (2×10 mL). The combined organic layer was washed withbrine (5 mL), dried (MgSO₄), concentrated, and purified by flashchromatography (silica, ethylacetate) to give 41 (43.5 mg, 95%) as awhite solid.

Physical Data for Acetate 41. R_(f)=0.61 (silica, ethylacetate); IR(film) v_(max) 3470, 3327, 2955, 2881, 1731, 1675, 1592, 1370, 1279,1229, 1108, 822, 738 cm⁻¹; ¹H NMR (500 MHz, CDCl₃) δ9.23 (br s, 1 H,pyridine), 8.79 (br s, 1 H, pyridine), 8.30 (ddd, J=8.0, 2.0, 2.0 Hz, 1H, pyridine), 7.43 (dd, J=8.0, 5.0 Hz, 1 H, pyridine), 6.58 (s, 1 H,10-H), 5.70 (dd, J=6.5, 1.0 Hz, 1 H, 2-H), 4.91 (dd, J=9.5, 2.0 Hz, 1 H,5-H), 4.47 (dd, J=10.5, 7.0 Hz, 1 H, 7-H), 4.28 (d, J=8.0 Hz, 1 H,20-H), 4.11 (d, J=8.0 Hz, 1 H, 20-H), 3.91 (d, J=6.5 Hz, 1 H, 3-H), 2.93(d, J=20.0 Hz, 1 H, 14-H), 2.68 (dd, J=20.0, 1.0 Hz, 1 H, 14-H), 2.53(ddd, J=14.5, 9.5, 7.0 Hz, 1 H, 6-H), 2.24 (br s, 1 H, OH), 2.22 (s, 3H, De), 2.18 (s, 3 H, Me), 2.17 (s, 3 H, Me), 1.85 (ddd, J=14.5, 10.5,2.0 Hz, 1 H, 6-H), 1.66 (s, 3 H, Me), 1.26 (s, 3 H, Me), 1.18 (s, 3 H,Me), 0.90 (t, J=8.0 Hz, 9 H, OSi(CH₂CH₃)₃), 0.63-0.51 (band, 6 H,OSi(CH₂CH₃)₃); FAB HRMS (NBA/CsI) m/e 832.2145, M+Cs⁺ calcd for C₃₆H₄₉O₁₁NSi 832.2129.

Alcohol 42. A solution of enone 41 (39.8 mg, 0.0569 mmol) in MeOH-THF(5:1, 3.1 mL) at 0° C. was treated with NaBH₄ (65.0 mg, 1.72 mmol, addedby portions) and stirred for 1.5 h. The reaction mixture was dilutedwith ethylacetate (10 mL), treated with aqueous NH₄Cl (5 mL), andstirred for 10 min. The organic layer was separated and the aqueouslayer was extracted with ethylacetate (2×10 mL). The combined organiclayer was washed with brine (5 mL), dried (MgSO₄), concentrated, andpurified by flash chromatography (silica, ethylacetate) to give 41 (3.7mg, 9%) and 42 (24.3 mg, 67% based on 91% conversion) as an amorphoussolid.

Physical Data for Alcohol 42. R_(f)=0.42 (silica, ethylacetate); IR(film) v_(max) 3490, 2953, 2881, 1727, 1592, 1369, 1235, 1110, 822, 740cm⁻¹; ¹H NMR (500 MHz, CDCl₃) δ9.30 (d, J=2.0 Hz, 1 H, pyridine), 8.81(dd, J=5.0, 2.0 Hz, 1 H, pyridine), 8.35 (ddd, J=8.0, 2.0, 2.0 Hz, 1 H,pyridine), 7.44 (dd, J=8.0, 5.0 Hz, 1 H, pyridine), 6.46 (s, 1 H, 10-H),5.64 (d, J=7.0 Hz, 1 H, 2-H), 4.96 (dd, J=9.5, 1.5 Hz, 1 H, 5-H), 4.83(br dd, J=12.5, 7.5 Hz, 1 H, 13-H), 4.49 (dd, J=10.5, 6.5 Hz, 1 H, 7-H),4.28 (d, J=8.0 Hz, 1 H, 20-H), 4.15 (d, J=8.0 Hz, 1 H, 20-H), 3.89 (d,J=7.0 Hz, 1 H, 3-H), 2.53 (ddd, J=14.5, 9.5, 6.5 Hz, 1 H, 6-H),2.30-2.20 (m, 2 H, 14-CH₂), 2.28 (s, 3 H, Me), 2.19 (d, J=1.0 Hz, 3 H,18-Me), 2.18 (s, 3 H, Me), 1.87 (ddd, J=14.5, 10.5, 2.0 Hz, 1 H, 6-H),1.68 (s, 3 H, Me), 1.63 (br s, 2 H, OH, OH), 1.19 (s, 3 H, Me), 1.04 (s,3 H, Me), 0.92 (t, J=8.0 Hz, 9 H, OSi(CH₂CH₂)₃), 0.64-0.51 (band, 6 H,OSi(CH₂CH₃)₃); FAB HRMS (NBA/CsI) m/e 834.2270, M+Cs⁺ calcd for C₃₆H₅₁O₁₁NSi 834.2286.

DiTES taxoid 43. To a solution of alcohol 42 (12.6 mg, 0.018 mmol,previously azeotroped twice with benzene) and β-lactam 24 (17.0 mg,0.0446 mmol, previously azeotroped twice with benzene) in THF (0.97 mL)at 0° C., prepared from the Ojima-Holton protocol (Holton, R. A. ChemAbstr. 1990, 114, 164568q; Ojima, I.; Habus, I.; Zhao, M.; Georg, G. I.;Jayasinghe, L. R. J. Org. Chem. 1991, 56, 1681-1683; Ojima, I.; Habus,I.; Zhao, M.; Zucco, M.; Park, Y. H.; Sun, C. M.; Brigaud, T.Tetrahedron 1992, 48, 6985-7012), was added NaN(SiMe₃)₂ (0.054 mL of a1.0 M solution in THF, 0.054 mmol) dropwise. The resulting solution wasstirred for 0.5 h and poured into a mixture of ethylacetate (10 mL) andaqueous NH₄Cl (5 mL). The organic layer was separated and the aqueouslayer was extracted with ethylacetate (2×5 mL). The combined organiclayer was washed with brine (5 mL), dried (MgSO₄), concentrated, andpurified by flash chromatography (silica, 50→95% ethylacetate inhexanes) to give 42 (1.0 mg, 8%) and 43 (8.6. mg, 48% based on 92%conversion) as a white solid.

Physical Data for DiTES taxoid 43. R_(f)=0.40 (silica, 50% ethylacetatein hexanes); IR (film) v_(max) 3433, 2955, 2880, 1730, 1662, 1370, 1238,1112, 1018, 985, 824, 740 cm⁻¹; ¹H NMR (500 MHz, CDCl₃) δ9.34 (d, J=2.0Hz, 1 H, pyridine), 8.82 (dd, J=5.0, 2.0 Hz, 1 H, pyridine), 8.42 (ddd,J=8.0, 2.0, 2.0 Hz, 1 H, pyridine), 7.74-7.69 (m, 2 H), 7.51-7.20 (band,9 H), 7.08 (d, J=9.0 Hz, 1 H, NH), 6.46 (s, 1 H, 10-H), 6.22 (br t,J=9.0 Hz, 1 H, 13-H), 5.74-5.66 (m, 2 H, 2-H, 3′-H), 4.95 (dd, J=9.5,2.0 Hz, 1 H, 5-H), 4.70 (d, J=2.0 Hz, 1 H, 2′-H), 4.48 (dd, J=10.5,6.5Hz, 1 H, 7-H), 4.30 (d, J=8.0 Hz, 1 H, 20-H), 4.21 (d, J=8.0 Hz, 1 H,20-H), 3.86 (d, J=7.0 Hz, 1 H, 3-H), 2.58-2.48 (m, 1 H, 6-H), 2.54 (s, 3H, Me), 2.40 (dd, J=15.5, 9.0 Hz, 1 H, 14-H), 2.17 (s, 3 H, Me), 2.14(dd, J=15.5, 9.0 Hz, 1 H, 14-H), 2.03 (br s, 3 H, Me), 1.95-1.86 (m, 1H, 6-H), 1.73 (s, 4 H, Me, OH), 1.22 (s, 3 H, Me), 1.18 (s, 3 H, Me),0.93 (t, J=8.0 Hz, 9 H, OSi(CH₂Cl₃)₃), 0.82 (t, J=8.0 Hz, 9 H,OSi(CH₂CH₃)₃), 0.65-0.37 (band, 12 H, OSi(CH₂CH₃)₃, OSi(CH₂CH₃)₃); FABHRMS (NBA/CsI) m/e 1215.4066, M+Cs⁺ calcd for C₅₈H₇₈O₁₄N₂Si₂ 1215.4046.

Taxoid 44. A solution of silyl ether 43 (6.4 mg, 0.0059 mmol) in THF(0.4 mL) at 25° C. was treated with HF-pyridine (0.160 mL) and stirredfor 1.25 h. The reaction mixture was poured into a mixture ofethylacetate (10 mL) and aqueous NaHCO₃ (5 mL) and the resulting mixturewas stirred for 10 min. The organic layer was separated and the aqueouslayer was extracted with ethylacetate (2×10 mL). The combined organiclayer was washed with brine (5 mL), dried (MgSO₄), concentrated, andpurified by preparative TLC (silica, ethylacetate) to give 44 (3.8 mg,75%) as a colorless film.

Physical Data for Taxoid 44. R_(f)=0.59 (silica, ethylacetate); IR(film) v_(max) 3396, 2928, 1728, 1644, 1371, 1273, 1241, 1111, 1071cm⁻¹; ¹H NMR (500 MHz, CDCl₃) δ9.34 (br s, 1 H, pyridine), 8.83 (br d,J=3.5 Hz, 1 H, pyridine), 8.41 (br d, J=8.0 Hz, 1 H, pyridine),7.75-7.68 (m, 2 H), 7.53-7.34 (band, 9 H), 6.91 (d, J=9.0 Hz, 1 H, NH),6.27 (s, 1 H, 10-H), 6.23 (br t, J=9.0 Hz, 1 H, 13-H), 5.78 (dd, J=9.0,2.5 Hz, 1 H, 3′-H), 5.69 (d, J=7.0 Hz, 1 H, 2-H), 4.95 (dd, J=9.5, 2.0Hz, 1 H, 5-H), 4.79 (dd, J=5.5, 2.5 Hz, 1 H, 2′-H), 4.41 (ddd, J=11.0,6.5, 4.0 Hz, 1 H, 7-H), 4.29 (d, J=8.5 Hz, 1 H, 20-H), 4.20 (d, J=8.5Hz, 1 H, 20-H), 3.82 (d, J=7.0 Hz, 1 H, 3-H), 3.54 (d, J=5.5 Hz, 1 H,2′-OH), 2.56 (ddd, J=14.5, 9.5, 6.5 Hz, 1 H, 6-H), 2.49 (d, J=4.0 Hz, 1H, 7-OH), 2.43-2.26 (m, 2 H, 14-CH₂), 2.38 (s, 3 H, Me), 2.24 (s, 3 H,Me), 1.89 (ddd, J=14.5, 11.0, 2.0 Hz, 1 H, 6-H), 1.83 (s, 1 H, OH), 1.82(s, 3 H, Me), 1.69 (s, 3 H, Me), 1.25 (s, 3 H, Me), 1.14 (s, 3 H, Me);FAB HRMS (NBA/CsI) m/e 987.2325, M+Cs⁺ calcd for C₄₆H₅₀O₁₄N₂ 987.2316.

Preparation of 4-N, N-dimethylaniline-C-2 taxol (48)

Acetate 45. A solution of alcohol 18 (50.0 mg, 0.0714 mmol) and4-dimethylaminopyridine (DMAP, 26.0 mg, 0.213 mmol) in CH₂Cl₂ (3.0 mL)at 25° C. was treated with acetic anhydride (0.250 mL, 2.65 mmol) andstirred for 2.5 h. The reaction mixture was diluted with CH₂Cl₂ (10 mL),treated with aqueous NaHCO₃ (7 mL), and stirred vigorously for 25 min.The organic layer was separated and the aqueous layer was extracted withCH₂Cl₂ (2×10 mL). The combined organic layer was washed with brine (5mL), dried (MgSO₄), concentrated, and purified by flash chromatography(silica, 10% ethylacetate in benzene) to give 45 (41.0 mg, 77%) as anamorphous solid.

Physical Data for Acetate 45. R_(f)=0.27 (silica, 35% ethylacetate inhexanes); IR (film) v_(max) 3425, 2945, 1722, 1674, 1605, 1365, 1275,1232, 1179, 1094; ¹H NMR (500 MHz, CDCl₃) δ7.89 (d, J=9.0 Hz, 2 H, Ar),6.64 (d, J=9.0 Hz, 2 H, Ar), 6.56 (s, 1 H, 10-H), 5.64 (d, J=6.5 Hz, 1H, 2-H), 4.90 (br d, J=8.0 Hz, 1 H, 5-H), 4.45 (dd, J=10.5, 7.0 Hz, 1 H,7-H), 4.36 (d, J=9.0 Hz, 1 H, 20-H), 4.11 (d, J=9.0 Hz, 1 H, 20-H), 3.85(d, J=6.5 Hz, 1 H, 3-H), 3.05 (s, 6 H, NMe₂), 2.90 (d, J=20.0 Hz, 1 H,14-H), 2.62 (d, J=20.0 Hz, 1 H, 14-H), 2.51 (ddd, J=14.0, 8.0, 7.0, 1 H,6-H), 2.20 (s, 3 H, Me), 2.16 (s, 3 H, Me), 2.15 (s, 3 H, Me), 2.04 (s,1 H, OH), 1.84 (ddd, J=14.0, 10.5, 2.0 Hz, 1 H, 6-H), 1.63 (s, 3 H, Me),1.23 (s, 3 H, Me), 1.16 (s, 3 H, Me), 0.89 (t, J=8.0 Hz, 9 H,OSi(CH₂CH₃)₃), 0.58-0.53 (band, 6 H, OSi(CH₂CH₃)₃); FAB HRMS (NBA/CsI)m/e 874.8589, M+Cs⁺ calcd for C₃₉H₅₅O₁₁NSi 874.8594.

Alcohol 46. A solution of enone 45 (40.0 mg, 0.0539 mmol) in MeOH-THF(5.8:1, 4.1 mL) at 0° C. was treated with NaBH₄ (30.2 mg, 0.80 mmol,added by portions), stirred for 1 h, allowed to warm to 25° C. andstirred for 1.5 h. The reaction mixture was diluted with CH₂Cl₂ (15 mL),treated with aqueous NH₄Cl (5 mL), and stirred for 10 min. The organiclayer was separated and the aqueous layer was extracted with CH₂Cl₂(2×10 mL). The combined organic layer was washed with brine (5 mL),dried (MgSO₄), concentrated, and purified by flash chromatography(silica, 25→50% ethylacetate in petroleum ether) to give 45 (6.0 mg,15%) and 46 (30.0 mg, 88% based on 85% conversion) as an amorphoussolid.

Physical Data for Alcohol 46. R_(f)=0.30 (silica, 50% ethylacetate inpetroleum ether); ¹H NMR (500 MHz, CDCl₃) δ7.93 (d, J=9.0 Hz, 2 H, Ar),6.64 (d, J=9.0 Hz, 2 H, Ar), 6.42 (s, 1 H, 10-H), 5.57 (d, J=7.0 Hz, 1H, 2-H), 4.94 (br d, J=8.0 Hz, 1 H, 5-H), 4.83-4.75 (m, 1 H, 13-H), 4.46(dd, J=10.5, 6.5 Hz, 1 H, 7-H), 4.34 (d, J=8.5 Hz, 1 H, 20-H), 4.13 (d,J=8.5 Hz, 1 H, 20-H), 3.82 (d, J=7.0 Hz, 1 H, 3-H), 3.04 (s, 6 H, Me₂N),2.54-2.44 (m, 1 H, 6-H), 2.26 (s, 3 H, Me), 2.23 (d, J=7.5 Hz, 2 H,14-CH₂), 2.16 (s, 6 H, Me, Me), 2.08 (d, J=4.5 Hz, 1 H, OH), 1.89-1.80(m, 2 H, 6-H, OH), 1.64 (s, 3 H, Me), 1.16 (s, 3 H, Me), 1.01 (s, 3 H,Me), 0.89 (t, J=8.5 Hz, 9 H, OSi(CH₂Cl₃)₃), 0.62-0.48 (band, 6 H,OSi(CH₂CH₃)₃).

DiTES taxoid 47. To a solution of alcohol 46 (14.0 mg, 0.0188 mmol,previously azeotroped twice with benzene) and β-lactam 24 (25.0 mg,0.0656 mmol, previously azeotroped twice with benzene) in THF (0.75 mL)at 0° C., prepared from the Ojima-Holton protocol (Holton, R. A. ChemAbstr. 1990, 114, 164568q; Ojima, I.; Habus, I.; Zhao, M.; Georg, G. .;Jayasinghe, L. R. J. Org. Chem. 1991, 56, 1681-1683; Ojima, I.; Habus,I.; Zhao, M.; Zucco, M.; Park, Y. H.; Sun, C. M.; Brigaud, T.Tetrahedron 1992, 48, 6985-7012), was added NaN(SiMe₃)₂ (0.056 mL of a1.0 M solution in THF, 0.056 mmol) dropwise. The resulting solution wasstirred for 20 min and poured into a mixture of CH₂Cl₂ (10 mL) andaqueous NH₄Cl (5 mL). The organic layer was separated and the aqueouslayer was extracted with CH₂Cl₂ (2×5 mL). The combined organic layer waswashed with brine (5 mL), dried (MgSO₄), concentrated, and purified byflash chromatography (silica, 10→15% ethylacetate in benzene, then 50%ethylacetate in petroleum ether) to give 47 (12.0 mg, 57%) as a whitesolid.

Physical Data for DiTES taxoid 47. R_(f)=0.26 (silica, 15% ethylacetatein PhH); IR (film) V_(max) 3425, 2946, 2882, 1722, 1669, 1600, 1365,1275, 1238, 1179, 1094 cm⁻¹; ¹H NMR (500 MHz, CDCl₃) δ7.96 (d, J=9.0 Hz,2 H, Ar), 7.77-7.72 (m, 2 H), 7.54-7.26 (band, 8 H), 7.12 (d, J=8.5 Hz,1 H, NH), 6.69 (d, J=9.0 Hz, 2 H), 6.43 (s, 1 H, 10-H), 6.23 (br t,J=9.0 Hz, 1 H, 13-H), 5.68-5.63 (m, 2 H, 2-H, 3′-H), 4.93 (br d, J=8.0Hz, 1 H, 5-H), 4.67 (d, J=2.0 Hz, 1 H, 2′-H), 4.45 (dd, J=10.5 Hz, 6.5Hz, 1 H, 7-H), 4.36 (d, J=8.5 Hz, 1 H, 20-H), 4.20 (d, J=8.5 Hz, 1 H,20-H), 3.78 (d, J=7.0 Hz, 1 H, 3-H), 3.04 (s, 6 H, Me₂N), 2.55-2.46 (m,1 H, 6-H), 2.53 (s, 3 H, OAc), 2.36 (dd, J=15.5, 9.0 Hz, 1 H, 14-H),2.15 (s, 3 H, Me), 2.09 (dd, J=15.5, 9.0 Hz, 1 H, 14-H), 2.00 (d, J=1.0Hz, 3 H, Me), 1.92-1.84 (m, 2 H, 6-H, OH), 1.67 (s, 3 H, Me), 1.20 (s, 3H, 5 Me), 1.16 (s, 3 H, Me), 0.90 (t, J=8.0 Hz, 9 H, OSi(CH₂CH₃)₃), 0.79(t, J=8.0 Hz, 9 H, OSi(CH₂CH₃)₃), 0.63-0.35 (band, 12 H, OSi(CH₂CH₃)₃);FAB HRMS (NBA/CsI) m/e 1257.4503, M+Cs⁺ calcd for C₆₁H₈₄O₁₄N₂Si₂1257.4515.

Taxoid 48. A solution of silyl ether 47 (12.0 mg, 0.0107 mmol) in THF(1.0 mL) at 25° C. was treated with HF•pyridine (0.05 mL) and stirredfor 1.5 h. The reaction mixture was poured into a mixture ofethylacetate (10 mL) and aqueous NaHCO₃ (5 mL) and the resulting mixturewas stirred for 10 min. The organic layer was separated and the aqueouslayer was extracted with ethylacetate (2×10 mL). The combined organiclayer was washed with brine (5 mL), dried (MgSO₄), concentrated, andpurified by flash chromatography (silica, 50→75% ethylacetate inpetroleum ether) to give 48 (8.0 mg, 84%) as a colorless film.

Physical Data for Taxoid 48. R_(f)=0.44 (silica, 75% ethylacetate inpetroleum ether); IR (film) V_(max) 3414, 2914, 2850, 1722, 1664, 1660,1371, 1275, 1243, 1179 cm⁻¹; ¹H NMR (500 MHz, CDCl₃) δ7.95 (d, J=9.0 Hz,2 H), 7.77-7.72 (m, 2 H), 7.55-7.30 (band, 8 H), 7.03 (d, J=9.0 Hz, 1 H,NH), 6.67 (d, J=9.0 Hz, 2 H), 6.24 (s, 1 H, 10-H), 6.20 (br t, J=9.0 Hz,1 H, 13-H), 5.76 (dd, J=9.0, 2.5 Hz, 1 H, 3′-H), 5.62 (d, J=7.0 Hz, 1 H,2-H), 4.93 (br d, J=7.5 Hz, 1 H, 5-H), 4.76 (dd, J=5.0, 2.5 Hz, 1 H,2′-H), 4.37 (ddd, J=11.5, 6.5, 4.0 Hz, 1 H, 7-H), 4.34 (d, J=8.5 Hz, 1H, 20-H), 4.18 (d, J=8.5 Hz, 1 H, 20-H), 3.73 (d, J=7.0 Hz, 1 H, 3-H),3.57 (d, J=5.0 Hz, 1 H, 2′-OH), 3.04 (s, 6 H, Me₂N), 2.58-2.48 (m, 1 H,6-H), 2.44 (d, J=4.0 Hz, 1 H, 7-OH), 2.37 (s, 3 H, Me), 2.30-2.25 (m, 2H, 14-CH₂), 2.22 (s, 3 H, Me), 1.95 (s, 1 H, OH), 1.88-1.81 (m, 1 H,6-H), 1.74 (d, J=1.0 Hz, 3 H, Me), 1.65 (s, 3 H, Me), 1.21 (s, 3 H, Me),1.11 (s, 3 H, Me); FAB HRMS (NBA/CsI) m/e 1029.2760, M+Cs⁺ calcd forC₄₉H₅₆N₂O₁₄ 1029.2786.

Preparation of 1-naphthalene-C-2-taxol (52)

Acetate 49. A solution of previous alcohol 19 and4-dimethylaminopyridine (DMAP, 100 mg, 0.819 mmol) in CH₂Cl₂ (3 mL) at25° C. was treated with acetic anhydride (0.50 mL, 5.30 mmol) andstirred for 3 h. The reaction mixture was diluted with CH₂Cl₂ (5 mL),treated with aqueous NaHCO₃ (7 mL), and stirred vigorously for 25 min.The organic layer was separated and the aqueous layer was extracted withCH₂Cl₂ (2×10 mL). The combined organic layer was washed with brine (5mL), dried (MgSO₄), concentrated, and purified by preparative TLC(silica, 10% ethylacetate in benzene) to give 49 (54.1 mg, 89% fromcarbonate 7) as an amorphous solid.

Physical Data for Acetate 49. R_(f)=0.27 (20% ethylacetate in petroleumether); IR (film) v_(max) 3416, 2953, 2879, 1726, 1676, 1370, 1224, 1089cm⁻¹; ¹H NMR (500 MHz, CDCl₃) δ8.66 (s, 1 H, naphthalene), 8.06 (dd, 1H, J=9.0, 2.0 Hz, naphthalene), 7.98-7.89 (m, 3 H, naphthalene),7.68-7.55 (m, 2 H, naphthalene), 6.61 (s, 1 H, 10-H), 5.75 (d, J=7.0 Hz,1 H, 2-H), 4.95 (br d, J=8.0 Hz, 1 H, 5-H), 4.50 (dd, J=10.5, 7.0 Hz, 1H, 7-H), 4.35 (d, J=8.5 Hz, 1 H, 20-H), 4.16 (d, J=8.5 Hz, IH, 20-H),3.96 (d, J=8.5 Hz, 1 H, 20-H), 3.96 (d, J=7.0 Hz, 1 H, 3-H), 3.03 (d,J=20.0 Hz, 1 H, 14-H), 2.70 (d, J=20.0 Hz, 1 H, 14-H), 2.61-2.50 (m, 2H, 6-H, OH), 2.27 (s, 3 H, Me), 2.24 (s, 3 H, Me), 2.21 (s, 3 H, Me),1.91-1.83 (m, 1 H, 6-H), 1.70 (s, 3 H, Me), 1.30 (s, 3 H, Me), 1.20 (s,3 H, Me), 0.93 (t, J=8.0 Hz, 9 H, OSi(CH₂CH₃)₃), 0.66-0.57 (band, 6 H,OSi(CH₁CH₃)₃); FAB HRMS (NBA/CsI) m/e 881.2326, M+Cs⁺ calcd forC₄₁H₅₂O₁₁Si 881.2333.

Alcohol 50. A solution of enone 49 (54.1 mg, 0.0722 mmol) in MeOH (10mL) at 25° C. was treated with NaBH₄ (54.5 mg, 1.44 mmol, added byportions) and stirred for 2.0 h. The reaction mixture was diluted withCH₂Cl₂ (10 mL), treated with aqueous NH₄Cl (5 mL), and stirred for 10min. The organic layer was separated and the aqueous layer was extractedwith CH₂Cl₂ (2×10 mL). The combined organic layer was washed with brine(5 mL), dried (MgSO₄), concentrated, and purified by preparative TLC(silica, 20% ethylacetate in petroleum ether) to give 50 (26 mg, 48% )as an amorphous solid.

Physical Data for Alcohol 50. R_(f)=0.12 (20% ethylacetate in petroleumether); IR (film) v_(max) 3524, 2953, 1719, 1369, 1231, 1093, 829 cm⁻¹;¹H NMR (500 MHz, CDCl₃) δ8.70 (s, 1 H, naphthalene), 8.11 (dd, J=8.5,1.5 Hz, 1 H, naphthalene), 7.96-7.86 (m, 3 H, naphthalene), 7.65-7.54(m, 2 H, naphthalene), 6.45 (s, 1 H, 10-H), 5.68 (d, J=7.0 Hz, 1 H,2-H), 4.98 (br d, J=8.0 Hz, 1 H, 5-H), 4.884.81 (m, 1 H, 13-H), 4.51(dd, J=10.5, 7.0 Hz, 1 H, 7-H), 4.34 (d, J=8.5 Hz, 1 H, 20-H), 4.19 (d,J=8.5 Hz, 1 H, 20-H), 3.93 (d, J=7.0 Hz, 1 H, 3-H), 2.58-2.50 (m, 1,6-H), 2.41-2.14 (m, 3 H, 14-CH₂, 13-OH), 2.37 (s, 3 H, Me), 2.21 (br s,3 H, Me), 2.19 (s, 3 H, Me), 1.92-1.84 (m, 1 H, 6-H), 1.72 (s, 1 H, OH)1.71 (s, 3 H, Me), 1.22 (s, 3 H, Me), 1.05 (s, 3 H, Me), 0.93 (t, J=8.0Hz, 9 H, OSi(CH₂Cl₃)₃), 0.65-0.51 (band, 6 H, OSi(CH₂CH₃)₃); FAB HRMS(NBA/CsI) m/e 883.2484, M+Cs⁺ calcd for C₄₁H₅₄O₁₁Si 883.2490.

DiTES taxoid 51. To a solution of alcohol 50 (20.0 mg, 0.0266 mmol,previously azeotroped twice with benzene) and β-lactam 24 (20.0 mg,0.0525 mmol, previously azeotroped twice with benzene) in THF (1.1 mL)at −78° C., prepared from the Ojima-Holton protocol (Holton, R. A. ChemAbstr. 1990, 114, 164568q; Ojima, I.; Habus, I.; Zhao, M.; Georg, G. I.;Jayasinghe, L. R. J. Org. Chem. 1991, 56, 1681-1683; Ojima, I.; Habus,I.; Zhao, M.; Zucco, M.; Park, Y. H.; Sun, C. M.; Brigaud, T.Tetrahedron 1992, 48, 6985-7012), was added NaN(SiMe₃)₂ (0.065 mL of a1.0 M solution in THF, 0.065 mmol) dropwise. The resulting solution wasstirred for 10 min and poured into a mixture of CH₂Cl₂ (10 mL) andaqueous NH₄Cl (5 mL). The organic layer was separated and the aqueouslayer was extracted with CH₂Cl₂ (2×5 mL). The combined organic layer waswashed with brine (5 mL), dried (MgSO₄), concentrated, and purified bypreparative TLC (silica, 20% ethylacetate in petroleum ether) to give 51(18.7 mg, 62%) as a white solid.

Taxoid 52. A solution of silyl ether 51 (18.7 mg, 0.0165 mmol) in THF (2mL) at 25° C. was treated with HF•pyridine (1 mL) and stirred for 1 h.The reaction mixture was poured into a mixture of ethylacetate (10 mL)and aqueous NaHCO₃ (5 mL) and the resulting mixture was stirred for 10min. The organic layer was separated and the aqueous layer was extractedwith ethylacetate (2×10 mL). The combined organic layer was washed withbrine (5 mL), dried (MgSO₄), concentrated, and purified by preparativeTLC (silica, 50% ethylacetate in petroleum ether) to give 52 (12.8 mg,86%) as a colorless film.

Physical Data for Taxoid 52. R_(f)=0.16 (silica, 50% ethylacetate inpetroleum ether); IR (film) v_(max) 3420, 2967, 2896, 1721, 1652, 1519,1370, 1233, 1073, 776 cm⁻¹; ¹H NMR (500 MHz, CDCl₃) δ8.67 (s, 1 H,naphthalene), 8.04 (dd, J=8.5, 1.5 Hz, 1 H, naphthalene), 7.95 (br d,J=8.5 Hz, 1 H, naphthalene), 7.87 (br d, J=9.0 Hz, 1 H), 7.81 (br d,J=8.5 Hz, IH), 7.65-7.61 (m, 2 H), 7.56-7.51 (m, 1 H), 7.49-7.22 (band,9 H), 6.94 (d, J=9.0 Hz, 1 H, NH), 6.23-6.16 (m, 2 H, 10-H, 13-H), 5.78(dd, J=9.0, 2.0 Hz, 1 H, 3′-H), 5.64 (br d, J=7.0 Hz, 1 H, 2-H), 4.87(br d, J=8.0 Hz, 1 H, 5-H), 4.78-4.72 (m, 1 H, 2′-H), 4.38-4.31 (m, 1 H,7-H), 4.24 (d, J=8.5 Hz, 1 H, 20-H), 4.16 (d, J=8.5 Hz, 1 H, 20-H), 3.76(d, J=7.0 Hz, 1 H, 3-H), 3.53 (br s, 1 H, OH), 2.52-2.43 (m, 1 H, 6-H),2.42 (d, J=4.0 Hz, 1 H, OH), 2.40 (s, 3 H, Me), 2.36 (dd, J=15.5, 9.0Hz, IH, 14-H), 2.25 (dd, J=15.5, 9.0 Hz, 1 H, 14-H), 2.17 (s, 3 H, Me),1.85-1.77 (m, 2 H, 6-H, OH), 1.74 (br s, 3 H, Me), 1.63 (s, 3 H, Me),1.17 (s, 3 H, Me), 1.09 (s, 3 H, Me); FAB HRMS (NBA/CsI) m/e 1036.2505,M+Cs⁺ calcd for C₅₁H₅₃NO₁₄ 1036.2520

Preparation of thioether-C-2 taxol (56)

Acetate 53. A solution of alcohol 23 (25.2 mg, 0.0351 mmol) and4-dimethylaminopyridine (DMAP, 12.2 mg, 0.0999 mmol) in CH₂Cl₂ (1.5 mL)at 25° C. was treated with acetic anhydride (0.120 mL, 1.27 mmol) andstirred for 1.5 h. The reaction mixture was diluted with CH₂Cl₂ (5 mL),treated with aqueous NaHCO₃ (7 mL), and stirred vigorously for 25 min.The organic layer was separated and the aqueous layer was extracted withCH₂Cl₂ (2×10 mL). The combined organic layer was washed with brine (5mL), dried (MgSO₄), concentrated, and purified by flash chromatography(silica, 30% ethylacetate in petroleum ether) to give 53 (25.3 mg, 95%)as a colorless oil.

Physical Data for Acetate 53. R_(f)=0.41 (silica, 10% ethylacetate inbenzene, 2 elutions); IR (film) v_(max) 3471, 2954, 2881, 1729, 1675,1370, 1226, 986, 824, 738 cm⁻¹; ¹H NMR (500 MHz, CDCl₃) δ7.38-7.25(band, 5 H, SPh), 6.54 (s, 1 H, 10-H), 5.49 (br d, J=6.5 Hz, 1 H, 2-H),4.90 (dd, J=9.5, 2.0 Hz, 1 H, 5-H), 4.42 (dd, J=10.5, 6.5 Hz, IH, 7-H),4.37 (d, J=8.0 Hz, 1 H, 20-H), 4.17 (d, J=8.0 Hz, 1 H, 20-H), 3.78 (d,J=6.5 Hz, 1 H, 3-H), 3.23-3.13 (m, 2 H, CH₂SPh), 2.78 (d, J=20.0 Hz, 1H, 14-H), 2.72-2.58 (m, 3 H, CH₂CH₂SPh, 14-H), 2.52 (ddd, J=14.5, 9.5,6.5, 1 H, 6-H), 2.45 (s, 1 H, OH), 2.21 (s, 3 H, Me), 2.15 (s, 3 H, Me),2.04 (s, 3 H, Me), 1.86 (ddd, J=10.5, 2.0 Hz, 1 H, 6-H), 1.62 (s, 3 H,Me), 1.23 (s, 3 H, Me), 1.19 (s, 3 H, Me), 0.91 (t, J=8.0 Hz, 9 H,OSi(CH₂CH₃)₃), 0.64-0.52 (band, 6 H, OSi(CH₂CH₃)₃); FAB HRMS (NBA/CsI)m/e 891.2225, M+Cs³⁰ calcd for C₃₉H₅₄O₁₁SSi 891.2210.

Alcohol 54. A solution of enone 53 (24.4 mg, 0.032 mmol) in MeOH-THF(5:1, 1.9 mL) at 0° C. was treated with NaBH₄ (18.1 mg, 0.48 mmol, addedby portions) and stirred for 1.25 h. The reaction mixture was dilutedwith CH₂Cl₂ (5 mL), treated with aqueous NH₄Cl (5 mL), and stirred for10 min. The organic layer was separated and the aqueous layer wasextracted with CH₂Cl₂ (2×5 mL). The combined organic layer was washedwith brine (5 mL), dried (MgSO₄), concentrated, and purified by flashchromatography (silica, 30% ethylacetate in hexanes) to give 54 (14.6mg, 60%) as an amorphous solid.

Physical Data for Alcohol 54. R_(f)=0.11 (silica, 30% ethylacetate inhexanes); IR (film) v_(max) 3487, 2938, 2880, 1729, 1586, 1369, 1234,977, 738 cm⁻¹; ¹H NMR (500 MHz, CDCl₃) δ7.40-7.23 (band, 5 H, SPh), 6.42(s, 1 H, 10-H), 5.43 (d, J=7.0 Hz, 1 H, 2-H), 4.94 (dd, J=9.5, 2.0 Hz, 1H, 5-H), 4.85-4.78 (m, 1 H, 13-H), 4.43 (dd, J=10.5, 6.5 Hz, 1 H, 7-H),4.37 (d, J=8.0 Hz, IH, 20-H), 4.18 (d, J=8.0 Hz, 1 H, 20-H), 3.74 (d,J=7.0 Hz, 1 H, 3-H), 3.25-3.15 (m, 2 H, CH₂SPh), 2.71-2.57 (m, 2 H,CH₂CH₂SPh), 2.51 (ddd, J=14.5, 9.5, 6.5 Hz, 1 H, 6-H), 2.25 (dd, J=15.5,9.5 Hz, 1 H, 14-H), 2.16 (s, 3 H, Me), 2.15 (d, J=1.0 Hz, 3 H, 18-Me),2.15 (s, 3 H, Me), 2.09 (dd, J=15.5, 7.0 Hz, 1 H, 14-H), 2.05 (br s, 1H, OH), 1.99-1.96 (m, 1 H, OH), 1.86 (ddd, J=14.5, 10.5, 2.0 Hz, 1 H,6-H), 1.63 (S, 3 H, Me), 1.15 (s, 3 H, Me), 1.04 (s, 3 H, Me), 0.91 (t,J=8.0 Hz, 9 H, OSi(CH₂CH₃)₃), 0.64-0.50 (band, 6 H Si(CH₂CH₄H₃)₃); FABHRMS (NBA/CsI) m/e 893.2350, M+Cs⁺ calcd for C₃₉H₅₆O₁₁SSi 893.2367.

DiTES taxoid 55. To a sulution of alcohol 54 (21.8 mg, 0.0286 mmol,prcviously azenti-oped twice with benzcnc) and β-lactam 24 (33.0 mg,0.0866 mmol, previously azentroped twice with benzene) in THF (1.1 mL)at 0° C., prepared from thc Ojima-Holton. protocol (Holton, R. A. ChemAbstr. 1990. 114, 164568q; Ojima, I.; Habus, I.; Zliao, M.- Georg, (C.T.: Jayasinghe, L. R. J. Org. Chem. 1991. 56, 1681-1683; Ojima, 1.;Habus, I.; Zhlao. M.: Zucco. M., Park, Y. H.; Sun, C. M..; Brigaud. T.Tetrnhedron 1992, 48, 6985-7012), was added NaN(SiMe₃)₂ (0.086 mL of a1.0 M solution in THF, 0.086 mmol) dropwise. The resulting solution wasstirred for 20 min and poured into a mixture of C₂Cl₂ (10 mL) andaqueous NH₄Cl (5 mL). The organic layer was separated and the aqueouslaycr was extracted with CH₂Cl₂ (2×5 mL). Thc combined organic layer waswashed with brine (5 mL), dried (MgSO₄), concentrated, and purified byflash chromatography (silica, 15→30→50% ethylacetate in petrolcum ether)to give 55 (13.8 mg, 42%) as an amorphous solid.

Physical Data for DiTES taxoid 55. R_(f)=0.40 (silica, 30% etylacetatein hexanes); IR (film) v_(max) 3437, 2952, 2879, 1735. 1662, 1482, 1369,1236, 1128, 981, 740 cm⁻¹; ¹H NMR (500 MHz, CDCl₃) δ7.82-7.76 (m, 2 H),7.54-7.16 (band, 13 H), 7.11 (d, J=9.0 Hz, 1 H, NH), 6.41 (s, 1 H,10-H), 6.18 ( hr r, J=9.0 Hz, 1 H, 13-H), 5.62 (dd, J=9.0, 2.0 Hz, 1 H,3′-H), 5.49 (d, J=7.0 Hz. IH, 2-H). 4.93 (dd, J=9.5, 2.0 Hz, 1 H, 5-II),4.64 (d. J=2.0 Hz, 1 H, 2-H), 4.42 (dd, J=10.5, 6.5 Hz. 1 H, 7-H), 4.40(d, J=8.0 Hz, 1 H, 20-H), 4.21 (d, J=8.0 Hz, 1 H, 20-H), 3.70 (d, J=7.0IIz, 1 H, 3-H) 3.23-3.17 (m, 2 H, CH₂SPh), 2.78 2.69 (m, 1 H,HCHCH₂SPh), 2.67-2.57 (m, 1 H, HCIICII₂SPh), 2.55-2.46 (m, 2 H, 6-H,OH), 2.38 (s, 3 H, Me), 2.27-2.10 (m, 2 H, 14-CH₂), 2.16 (s, 3 H, Me),1.98 (d. J=1.0 Hz, 3 H, Me), 1.89 (ddd, J=14.0, 11.0, 2.0 Hz, 1 H, 6-H),1.64 (s, 3 H, Me), 1.18 (s, 3 H, Me), 1.17 (s, 3 H, Me), 0.91 (t, J=8.0Hz, 9 H, OSi(CH₂CH₃)₃), 0.81 (t, J=8.0 Hz, 9 H, OSi(CII₂CH₃)₃),0.64-0.36 (band, 12 H, OSi(CH₂CII₃)₃); FAB HRMS (NBA/CsI) m/eM+Cs⁺1274.4125 calcd for C₆₁H₈₃O₁₄SSi₂ 1274.4127.

Taxoid 56. A solution of silyl ether 55 (8.1 mg, 0.0071 mmol) in THF(0.5 mL) at 25° C. was treated with HF•pyridine (0.150 mL) and stirredfor 3.75 h. The reaction mixture was poured into a mixture ofethylacetate (10 mL) and aqueous NaHCO₃ (5 mL) and the resulting mixturewas stirred for 10 min. The organic layer was separated and the aqueouslayer was extracted with ethylacetate (2×10 mL). The combined organiclayer was washed with brine (5 mL), dried (MgSO₄), concentrated, andpurified by preparative TLC (silica, 60% ethylacetate in petroleumether) to give 56 (3.2 mg, 49%) as a colorless film.

Physical Data for Taxoid 56. R_(f)=0.39 (silica, 60% ethylacetate inpetroleum ether); IR (film) v_(max) 3426, 2928, 1731, 1642, 1371, 1238,1070, 739, 709 cm⁻¹; ¹H NMR (500 MHz, CDCl₃) δ7.80-7.75 (m, 2 H),7.55-7.18 (band, 13 H), 6.94 (d, J=9.0 Hz, 1 H, NH), 6.23 (s, 1 H,10-H), 6.19 (br t, J=9.0 Hz, 1 H, 13-H), 5.74 (dd, J=9.0, 2.5 Hz, 1 H,3′-H), 5.47 (d, J=7.0 Hz, 1 H, 2-H), 4.93 (dd, J=9.5, 2.0 Hz, 1 H, 5-H),4.74 (dd, J=5.0, 2.5 Hz, 1 H, 2′-H), 4.38 (d, J=8.0 Hz, 1 H, 20-H), 4.35(ddd, J=11.0, 6.5 Hz,-4.5 Hz, 1 H, 7-H), 4.21 (d, J=8.0 Hz, 1 H, 20-H),3.67 (d, J=7.0 Hz, 1 H, 3-H), 3.51 (d, J=5.0 Hz, 1 H, 2′-OH), 3.28-3.14(m, 2 H, CH₂SPh), 2.77-2.68 (m, 1 H, HCHCH₂SPh), 2.67-2.59 (m, 1 H,HCHCH₂SPh), 2.54 (ddd, J=14.5, 9.5, 6.5 Hz, 1 H, 6-H), 2.44 (d, J=4.5Hz, 1 H, 7-OH), 2.36 (dd; J=15.5, 9.0 Hz, 1 H, 14-H), 2.26 (br s, 1 H,OH), 2.23 (s, 3 H, Me), 2.21 (s, 3 H, Me), 2.18 (dd, J=15.5, 9.0 Hz, 1H, 14-H), 1.88 (ddd, J=14.5, 11.0, 2.0 Hz, 1 H, 6-H), 1.75 (d, J=1.0 Hz,3 H, Me), 1.63 (s, 3 H, Me), 1.24 (s, 3 H, Me), 1.10 (s, 3 H, Me); FABHRMS (NBA/CsI) m/e 1046.2410, M+Cs⁺ calcd for C₄₉H₅₅O₁₄NS 1046.2398.

Preparation of MPA taxoid 57

MPA taxoid 57. A solution of taxoid 36 (4.3 mg, 0.005 mmol) andtriethylamine (0.0033 mL, 0.0237 mmol) in CH₂Cl₂ (0.2 mL) at 25° C. wastreated with 2-fluoro-1-methylpyridinium p-toluenesulfonate (2.1 mg,0.0075 mmol) and stirred for 35 min. The clear colorless solutionrapidly turned to a clear pale yellow. The course of the reaction wasmonitored through thin layer chromatography (TLC)(E. Merck RP- 18silica, 65 tetrahydrofuran: 35 water, UV/phospho-molybidic acid) andafter thirty minutes of stirring at ambient temperature, judged completeas no taxol remained and only one compound was apparent by TLC. Thereaction mixture was directly purified by HPLC (Vydak RP-18, 22.5×3 mm,A→B 0.5 h linear, A: 20% MeOH in 20 mM NH₄OAc, B: 100% MeOH, 9 mL/min,RT=26.12) to give 36 (0.8 mg, 19%) and 57 (4.1 mg, 100% based on 81%conversion) as a colorless film.

Physical Data for taxoid 57 ¹H NMR (500 MHz, CDCl₃) δ10.5 (d, J=7.5 Hz,1 H), 8.44 (ddd, J=9.0, 7.5, 2.0 Hz, 1 H), 8.33-8.29 (m, 2 H), 8.15 (dd,J=3.0, 1.0 Hz, 1 H, thiophene), 8.12 (br d, J=6.0 Hz, 1 H), 7.84 (br d,J=8.5 Hz, 1 H), 7.74-7.69 (m, 2 H), 7.53 (dd, J=5.0, 1.0 Hz, 1 H,thiophene), 7.48-7.34 (band, 7H), 7.16-7.12 (m, 1 H), 6.53-6.43 (m, 1 H,2′-H), 6.21 (s, 1 H, 10-H), 6.03 (dd, J=10.5, 8.0 Hz, 1 H, 3′-H), 5.82(br t, J=9.0 Hz, 1 H, 13-H), 5.44 (d, J=7.0 Hz, 1 H, 2-H), 4.90 (dd,J=9.5, 2.0 Hz, 1 H, 5-H), 4.33 (dd, J=11.0, 6.5 Hz, 1 H, 7-H), 4.30 (d,J=8.0 Hz, 1 H, 20-H), 4.15 (d, J=8.0 Hz, 1 H, 20-H), 4.08 (s, 3 H,N+Me), 3.68 (d, J=7.0 Hz, 1 H, 3-H), 2.58-2.49 (m, 1 H, 6-H), 2.52 (s, 3H, OAc), 2.21 (s, 3 H, OAc), 2.04 (s, 3 H, OAc), 2.02 (br s, 2 H, OH,OH), 1.88 (ddd, J=14.5, 11.5, 2.0 Hz, 1 H, 6-H), 1.78 (br s, 3 H,18-Me), 1.64 (s, 3 H, Me), 1.61 (dd, J=16.0, 7.0 Hz, 1 H, 14-H), 1.18(dd, J=16.0, 9.0 Hz, 1 H, 14-H), 1.13 (s, 3 H, Me), 1.08 (s, 3 H, Me).

Preparation of MPA taxoid 58

MPA taxoid 58. A solution of taxoid 32 (1.0 equiv.) and triethylamine(4.7 equiv.) in CH₂Cl₂ (0.025 M) at 25° C. is treated with2-fluoro-1-methylpyridinium p-toluenesulfonate from Aldrich Chemicalcompany inc. (1.5 equiv.) and stirred for 35 minutes. The course of thereaction was monitored through thin layer chromatography (TLC)(E. MerckRP- 18 silica, 65 tetrahydrofuran: 35 water, UV/phospho-molybidic acid)and after thirty minutes of stirring at ambient temperature, judgedcomplete as no taxol remained and only one compound was apparent by TLC.The reaction mixture is then directly purified by HPLC (Vydak RP- 18,22.5×3 mm, A→B 0.5 h linear, A: 20% MeOH in 20 mM NH₄OAc, B: 100% MeOH,9 mL/min, RT=26.12) to give 58 as a colorless film.

Preparation of MPA taxoid 59

MPA taxoid 59. The synthesis of the taxoid-7-MPA 59 differs onlyslightly from the synthesis of taxoid-2′-MPA 58. The C-2 taxoid 32 isdissolved in methylene chloride (0.006 M) and treated sequentially withtriethylamine (40 equivalents) and 2-fluoro-1-methyl-pyridinium tosylate(10 equivalents) Aldrich Chemicals, and allowed to stir at ambienttemperature for 5 minutes. The reaction mixture is then directlypurified by HPLC (Vydak RP-18, 22.5×3 mm, A→B 0.5 h linear, A: 20% MeOHin 20 mM NH₄OAc, B: 100% MeOH, 9 mL/min, RT=26.12) to give 59 as acolorless film.

Preparation of MPA taxoid 60

MPA taxoid 60. The synthesis of the taxoid-7-MPA 60 differs onlyslightly from the synthesis of taxoid-2′-MPA 57. The C-2 taxoid 36 isdissolved in methylene chloride (0.006 M) and treated sequentially withtriethylamine (40 equivalents) and 2-fluoro-1-methyl-pyridinium tosylate(10 equivalents) Aldrich Chemicals, and allowed to stir at ambienttemperature for 5 minutes. The reaction mixture is then directlypurified by HPLC (Vydak RP-18, 22.5×3 mm, A→B 0.5 h linear, A: 20% MeOHin 20 mM NH₄OAc, B: 100% MeOH, 9 mL/min, RT=26.12) to give 60 as acolorless film.

Preparation of C-2-taxoid-2′-methyl-pyridinium salts

C-2-taxoid-2′-onium salts 62-66. A solution of taxoid (62-66) 1. (1.0equiv.) and triethylamine (4.7 equiv.) in CH₂Cl₂ (0.025 M) at 25° C. istreated with 2-fluoro-1-methylpyridinium p-toluenesulfonate from AldrichChemical company inc. (1.5 equiv.) and stirred for 35 minutes. Thecourse of the reaction was monitored through thin layer chromatography(TLC)(E. Merck RP-18 silica, 65 tetrahydrofuran: 35 water,UV/phospho-molybidic acid) and after thirty minutes of stirring atambient temperature, judged complete as no taxol remained and only onecompound was apparent by TLC. The reaction mixture is then directlypurified by HPLC (Vydak RP-18, 22.5×3 mm, A→B 0.5 h linear, A: 20% MeOHin 20 mM NH₄OAc, B: 100% MeOH, 9 mL/min, RT=26.12) to give (62-66) II.as a colorless film.

Preparation of C-2-taxoid-7-methyl-pyridinium salts

C-2-taxoid-7-onium salts 67-72. The synthesis of thetaxoid-7-methyl-pyridinium salts (67-72) II, differs only slightly fromthe synthesis of taxoid-2′-methyl-pyridinium salts (62-66) II. The C-2taxoid (67-72) I is dissolved in methylene chloride (0.006 M) andtreated sequentially with triethylamine (40 equivalents) and2-fluoro-1-methyl-pyridinium tosylate (10 equivalents) AldrichChemicals, and allowed to stir at ambient temperature for 5 minutes. Thereaction mixture is then directly purified by HPLC (Vydak RP-18, 22.5×3mm, A→B 0.5 h linear, A: 20% MeOH in 20 mM NH₄OAc, B: 100% MeOH, 9mL/min, RT=26.12) to give (67-72) II as a colorless film.

Preparation of C-2-taxoid-bis-2′,7-methyl-pyridinium salts

C-2-taxoid-bis-2′,7-onium salts 73-80. The synthesis ofC-2-taxoid-bis-2′,7-methyl-pyridinium salts II (73-80), differs from thesynthesis of taxoid-7-methyl-pyridinium salts (67-72) II only withrespect to reaction time. The C-2 taxoid (73-80) I is dissolved inmethylene chloride (0.006 M) and treated sequentially with triethylamine(40 equivalents) and 2-fluoro-1-methyl-pyridinium tosylate (10equivalents) Aldrich Chemicals, and allowed to stir at ambienttemperature for 18 hours. The reaction mixture is then directly purifiedby HPLC (Vydak RP-18, 22.5×3 mm, A→B 0.5 h linear, A: 20% MeOH in 20 mMNH₄OAc, B: 100% MeOH, 9 mL/min, RT=26.12) to give (73-80) II as acolorless film.

Preparation of C-2-taxoid-2′-benzothiazolium salts

C-2-taxoid-2′-benzothiazolium salts 81-88. A solution of taxoid 81-88(1.0 equiv.) and triethylamine (4.7 equiv.) in CH₂Cl₂ (0.025 M) at 25°C. is treated with 2-fluoro-1-methylpyridinium p-toluenesulfonate fromAldrich Chemical company inc. (1.5 equiv.) and stirred for 35 minutes.The course of the reaction was monitored through thin layerchromatography (TLC)(E. Merck RP-18 silica, 65 tetrahydrofuran: 35water, UV/phospho-molybidic acid) and after thirty minutes of stirringat ambient temperature, judged complete as no taxol remained and onlyone compound was apparent by TLC. The reaction mixture is then directlypurified by HPLC (Vydak RP-18, 22.5×3 mm, A→B 0.5 h linear, A: 20% MeOHin 20 mM NH₄₀Ac, B: 100% MeOH, 9 mL/min. RT=26.12) to give 81-88 as acolorless film.

Preparation of C-2-taxoid-7-benzothiazolium salts

C-2-taxoid-7-benzothiazolium salts (89-96). The synthesis of thetaxoid-7-benzothiazolium salts (89-96) II, differs only slightly fromthe synthesis of taxoid-2′-benzothiazolium salts (81-88) II. The C-2taxoid (89-96) I is dissolved in methylene chloride (0.006 M) andtreated sequentially with triethylamine (40 equivalents) and2-fluoro-3-ethylbenzothiazolium tetrafluoroborate (10 equivalents)Aldrich Chemicals, and allowed to stir at ambient temperature for 5minutes. The reaction mixture is then directly purified by HPLC (VydakRP-18, 22.5×3 mm, A→B 0.5 h linear, A: 20% MeOH in 20 mM NH₄OAc, B: 100%MeOH, 9 mL/min, RT=26.12) to give (89-96) II as a colorless film.

Preparation of C-2-taxoid-2′-benzoxazolium salts

C-2-taxoid-2′-benzoxazolium salts 97-104. A solution of taxoid (97-104)I. (1.0 equiv.) and triethylamine (4.7 equiv.) in CH₂Cl₂ (0.025 M) at25° C. is treated with 2-chloro-3-ethylbenzoxazolium tetrafluoroboratefrom Aldrich Company (1.5 equiv.) and stirred for 35 minutes. The courseof the reaction was monitored through thin layer chromatography (TLC)(E.Merck RP-18 silica, 65 tetrahydrofuran: 35 water, UV/phospho-molybidicacid) and after thirty minutes of stirring at ambient temperature,judged complete as no taxol remained and only one compound was apparentby TLC. The reaction mixture is then directly purified by HPLC (VydakRP-18, 22.5×3 mm, A→B 0.5 h linear, A: 20% MeOH in 20 mM NH₄OAc, B: 100%MeOH, 9 mL/min, RT=26.12) to give (97-104) II. as a colorless film.

Preparation of C-2-taxoid-7-benzoxazolium salts

C-2-taxoid-7-benzoxazolium salts (105-112). The synthesis of thetaxoid-7-benzoxazolium salts (105-112) II, differs only slightly fromthe synthesis of taxoid-2′-benzoxazolium salts (97-104) II. The C-2taxoid (105-112) I is dissolved in methylene chloride (0.006 M) andtreated sequentially with triethylamine (40 equivalents) and2-chloro-3-ethylbenzoxazolium tetrafluoroborate from Aldrich Company (10equivalents) Aldrich Chemicals, and allowed to stir at ambienttemperature for 5 minutes. The reaction mixture is then directlypurified by HPLC (Vydak RP-18, 22.5×3 mm, A→B 0.5 h linear, A: 20% MeOHin 20 mM NH₄OAc, B: 100% MeOH, 9 mL/min, RT=26.12) to give (105-112) IIas a colorless film.

Preparation of C-2-taxoid-2′-pyrimidinium salts

C-2-taxoid-2′-pyrimidinium salts 113-120. A solution of taxoid (113-120)I. (1.0 equiv.) and triethylamine (4.7 equiv.) in CH₂Cl₂ (0.025 M) at25° C. is treated with 2-chloro-methyl-pyrimidinium fluoride fromAldrich Company (1.5 equiv.) and stirred for 35 minutes. The course ofthe reaction was monitored through thin layer chromatography (TLC)(E.Merck RP- 18 silica, 65 tetrahydrofuran: 35 water, UV/phospho-molybidicacid) and after thirty minutes of stirring at ambient temperature,judged complete as no taxol remained and only one compound was apparentby TLC. The reaction mixture is then directly purified by HPLC (VydakRP-18, 22.5×3 mm, A→B 0.5 h linear, A: 20% MeOH in 20 mM NH₄OAc, B: 100%MeOH, 9 mL/min, RT=26.12) to give (113-120) II. as a colorless film.

Preparation of C-2-taxoid-7-pyrimidinium salts

C-2-taxoid-7-pyrimidinium salts (121-128). The synthesis of thetaxoid-7-pyrimidinium salts (121-128) II, differs only slightly from thesynthesis of taxoid-2′-pyrimidinium salts (113-120) II. The C-2 taxoid(121-128) I is dissolved in methylene chloride (0.006 M) and treatedsequentially with triethylamine (40 equivalents) and2-chloro-methyl-pyrimidinium fluoride from Aldrich Company (10equivalents), and allowed to stir at ambient temperature for 5 minutes.The reaction mixture is then directly purified by HPLC (Vydak RP-18,22.5×3 mm, A→B 0.5 h linear, A: 20% MeOH in 20 mM NH₄OAc, B: 100% MeOH,9 mL/min, RT=26.12) to give (121-128) II as a colorless film.

What is claimed is:
 1. A cyclic method employing chemical switching forsolubilizing and desolubilizing a taxo-diterpenoid with respect to anaqueous solvent, an underivatized form of the taxo-diterpenoid having alow solubility and including a reactive C^(n)-hydroxyl, the methodcomprising the following steps: Step A: converting the underivatizedform of the taxo-diterpenoid from low solubility to high solubility byderivatizing the reactive C^(n)-hydroxyl with an onium salt of a2-halogenated aza-arene to form an onium salt of ataxo-diterpenoid-C^(n),2-O-aza-arene derivative having high solubility,wherein the onium salt of the 2-halogenated aza-arene is represented bvthe following structures I and II:

wherein: R⁰ is a halogen selected from the group consisting of Cl, Br,F, and I; Z¹ and Z² are each selected from the group consisting of C andN; Z³ is selected from the group consisting of S and O; R¹ is selectedfrom the goup consisting of C₁-C₆ alkyl, allyl, arenxyl, propargyl, andfused aryl; R² and R⁶ are each selected from the group consisting of H,C₁-C₆ alkyl, allyl, arenxyl, propargyl, and fused aryl; if Z¹ is C, thenR³ is selected from the group consisting of H, C₁-C₆ alkyl, allyl,arenxyl, proparyl, C₁-C₆ O-alkyl, OH, halogen, and fused aryl; if Z¹ isN, then R³ is absent; R⁴ and R⁸ are each selected from the groupconsisting of H, C₁-C₆ alkyl, allyl, arenxyl, propargyl, C₁-C₆ O-alkyl,OH, halogen, and fused aryl; and if Z² is C, then R⁵ is selected fromthe group consisting of H, C₁-C₆ alkyl, allyl, arenxyl, propargyl, C₁-C₆O-alkyl, OH, halogen, and fused aryl; if Z² is N, then R⁵ is absent, andS⁻ is a counter ion; and then Step B: converting the onium salt of thetaxo-diterpenoid-C^(n),2-O-aza-arene derivative produced in said Step Afrom high solubility by contacting thetaxo-diterpenoid-C^(n),2-O-aza-arene derivative with a serum protein fordisplacing the 2-O-aza-arene and forming a protein:taxo-diterpenoidintermediate, the protein:taxo-diterpenoid intermediate thendissociating to produce the underviatized form of the taxo-diterpenoidemployed in said Step A.
 2. A cyclic method employing chemical switchingfor solubilizing and desolubilizing a taxo-diterpenoid with respect toan aqueous solvent, an underivatized form of the taxo-diterpenoid havinga low solubility and including a reactive C^(n)-hydroxyl, the methodcomprising the following steps: Step A: converting the underivatizedform of the taxo-diterpenoid from low solubility to high solubility byderivatizing the reactive C^(n)-hydroxyl with an onium salt of a2-halogenated aza-arene to form an onium salt of ataxo-diterpenoid-C^(n),2-O-aza-arene derivate having high solubility,the underivatized form of the taxo-diterpenoid being represented byformula I as follows:

wherein: C^(n) is selected from the group consisting of C⁷ and C^(2′);R^(X) is selected from the group consisting of Ph and tBuO: R¹⁰ isselected from the group consisting of OAc and OH; and R^(y) selectedfrom the group consisting of benzyl and the following structures:

R^(2′) and R⁷ are each OH; the onium salt of thetaxo-diterpenoid-C^(n),2-O-aza-arene derivated produced in said Step Abeing represented by the above formula I wherein: R² and R⁷ are eachselected from the group consisting of OH and an onium salt of a2-O-aza-arene, with the proviso that at least one of R^(2′) and R⁷ issaid onium salt of the 2-O-aza-arene, said onium salt of the2-O-aza-arene being selected from the group consisitng of onium saltsrepresented by the following formulas II and III:

wherein: R⁰ is oxygen and is bonded to C^(n); Z¹ and Z² are eachselected from consisting of C and N; Z³ is selected from the groupconsisting of S and O; R¹ selected from the group consisting of C₁-C₆alkyl, allyl, arenxyl, propargyl, and fused aryl; R² and R⁶ are eachselected from the group consisting of H, C₁-C₆ alkyl, allyl, arenxyl,propargyl, and fused aryl; if Z¹ is C, then R³ is selected from thegroup consisting of H, C₁-C₆ alkyl, allyl, arenxyl, propargyl, C₁-C₆O-alkyl, OH, halogen, and fused aryl; if Z¹ is N, then R³ is absent; R⁴and R⁸ are each selected from the group consisting of H, C₁-C₆ alkyl,allyl, arenxyl, propargyl, C₁-C₆ O-alkyl, OH, halogen, and fused aryl;and if Z² is C, then R⁵ is selected from the group consisting of H,C₁-C₆ alkyl, allyl, arenxyl, propargyl, C₁-C₆ O-allkyl, OH, halogen, andfused aryl; if Z² is N, then R⁵ is absent; and S³¹ is a counter ion; andthe onium salt of the 2-halogenated aza-arene employed in said Step Abeing selected from the group consisting of onium salts represented bythe above indicated formulas II and III wherein: R⁰ is a halogenselected from the group consisting of Cl, Br, F, and I; and then Step B:converting the onium salt of the taxo-diterpenoid-C^(n),2-O-aza-arenederivate produced in said Step A from high solubility to low solubilityby contacting the taxo-diterpenoid-C^(n),2-O-aza-arene derivative with aserum protein for displacing the 2-O-aza-arene and forming aprotein:taxo-diterpenoid intermediate, the protein:taxo-diterpenoidintermediate then dissociating to produce the underviatized form of thetaxo-diterpenoid employed in said Step A.
 3. A cyclic method employingchemical switching for solubilizing and desolubilizing ataxo-diterpenoid with respect to an aqueous solvent, an underivatizedform of the taxo-diterpeniod having a low solubility and including areactive C^(n)-hydroxyl, the method comprising the following steps: StepA: converting the underivatized form of the taxo-diterpenoid from lowsolubility to high solubility by derivating the reactive C^(n)-hydroxylwith an onium salt of a 2-halogenated aza-arene to form an onium salt ofa taxo-diterpeniod-C^(n),2-O-aza-arene derivative having highsolubility, wherein the onium salt of the 2-halogenated aza-arene isrepresented by the following structures I and II:

wherein: R⁰ is a halogen selected from the group consisting of Cl, Br,F, and I; Z¹ and Z² are each selected from the group consisting of C andN; Z³ is selected from the group consisting of S and O; Z¹ is selectedfrom the group consisting of C₁-C₆ alkyl, allyl, arenxyl, propargyl, andfused aryl; R² and R⁶ are each selected from the group consisting of H,C₁-C₆ alkyl, allyl, arenxyl, propargyl, and fused aryl; if Z¹ is C, thenR³ is selected from the group consisting of H, C₁-C₆ alkyl, allyl,arenxyl, propargyl, C₁-C₆ O-alkyl, OH, halogen, and fused aryl; if Z¹ isN, then R³ is absent; R⁴ and R⁸ are each selected from the groupconsisting of H, C₁-C₆ alkyl, allyl, arenxyl, propargyl, C₁-C₆ O-alkyl,OH, halogen, and fused aryl; and if Z² is C, then R⁵ is selected fromthe group consisting of H, C₁-C₆ alkyl, allyl, arenxyl, propargyl, C₁-C₆O-alkyl, OH, halogen, and fused aryl; if Z² is N, then R⁵ is absent; andS⁻ is a counter ion; then Step B: contacting thetaxo-diterpenoid-C^(n),2-O-aza-arene derivative produced in said Step Awith serum protein for displacing the 2-O-aza-arene and forming aprotein:taxo-diterpenoid intermediate having a high solubility; and thenStep C: converting the taxo-diterpenoid:protein conjugate produced insaid Step B from high solubility to low solubility by releasing thetaxo-diterpeniod from the protein:taxo-diterpenoid conjugate to producethe underviatized form of the taxo-diterpenoid employed in said Step A.4. A method for solubilizing a taxo-diterpenoid with respect to anaqueous solvent, the taxo-diterpenoid including a reactiveC^(n)-hydroxyl, the method comprising the following step: Step A:converting the taxo-diterpenoid from low solubility to high solubilityby derivatizing the C^(n)-hydroxyl with an onium salt of a 2-halogenatedaza-arene to form an onium salt of ataxo-diterpenoid-C^(n),2-O-aza-arene derivative having high solubility,wherein the onium salt of the 2-halogenated aza-arene is represented bythe following structures I and II:

wherein: R⁰ is a halogen selected from the group consisting of Cl, Br,F, and I; Z¹ and Z² are each selected from the group consisting of C andN; Z³ is selected from the group consisting of S and O; R¹ is selectedfrom the group consisting of C₁-C₆ alkyl, allyl, arenxyl, propargyl, andfused aryl; R² and R⁶ are each selected from the group consisting of H,C₁-C₆ alkyl, allyl, arenxyl, propargyl, and fused aryl; if Z¹ is C, thenR³ is selected from the group consisting of H, C₁-C₆ alkyl, allyl,arenxyl, propargyl, C₁-C₆ O-alkyl, OH, halogen, and fused aryl; if Z¹ isN, then R³ is absent; R⁴ and R⁸ are each selected from the groupconsisting of H, C₁-C₆ alkyl, allyl, arenxyl, propargyl, C₁-C₆ O-alkyl,OH, halogen, and fused aryl; and if Z² is C, then R⁵ is selected fromthe group consisting of H, C₁-C₆ alkyl, allyl, arenxyl, propargyl, C₁-C₆O-alkyl, OH, halogen, and fused aryl; if Z² is N, then R⁵ is absent; andS⁻ is a counter ion.
 5. A method for solubilizing an underivatized formof a taxo-diterpenoid having a low solubility with respect to an aqueoussolvent, the underivated form of the taxo-diterpenoid including areactive C^(n)-hydroxyl, the method comprising the following steps: StepA: converting the underivatized form of the taxo-diterpenoid from lowsolubility to high solubility by derivatizing the reactiveC^(n)-hydroxyl with an onium salt of a 2-halogenated aza-arene to forman onium salt of a taxo-diterpenoid-C^(n),2-O-aza-arene derivativehaving high solubility, the underivatized form of the taxo-diterpeniodbeing represented by formula I as follows:

wherein: C^(n) is selected from the group of C⁷ and C^(2′); R^(X) isselected from the group consisting of Ph and tBuO; R¹⁰ is selected fromthe group consisting of OAc and OH; and R^(y) is selected from the groupconsisting of benzyl and the following structures:

R^(2′) and R⁷ are each OH; the onium salt of thetaxo-diterpenoid-C^(n),2-O-aza-arene derivative produced in said Step Abeing represented by the above formula I wherein: R^(2′) and R⁷ are eachselected from the group consisting of OH and an onium salt of a2-O-aza-arene, with the proviso that at least one of R^(2′) and R⁷ issaid onium salt of the 2-O-aza-arene, said onium salt of the2-O-aza-arene being selected from the group consisting of onium saltsrepresented by the following formulas II and III:

wherein: R⁰ is oxygen and is bonded to C^(n); Z¹ and Z² are eachselected from the group consisting of C and N; Z³ is selected from thegroup consisting of S and O; R¹ is selected from the group consisting ofC₁-C₆ alkyl, allyl, arenxyl, propargyl, and fused aryl; R² and R⁶ areeach selected from the group consisting of H, C₁-C₆ alkyl, allyl,arenxyl, progargyl, and fused aryl; if Z¹ is C, then R³ is selected fromthe group consistng of H, C₁-C₆ alkyl, allyl, arenxyl, propargyl, C₁-C₆O-alkyl, OH, halogen, and fused aryl; if Z¹ is N, then R³ is absent; R⁴and R⁸ are each selected from the group consisting of H, C₁-C₆ alkyl,allyl, arenxyl, propargyl, C₁-C₆ O-alkyl, OH, halogen, and fused aryl;and if Z² is C, then R⁵ is selected from the group consisting of H,C₁-C₆ alkyl, allyl, arenxyl, progargyl, C₁-C₆ O-alkyl, OH, halogen, andfused aryl; if Z² is N, then R⁵ is absent; and S⁻ is a counter ion; andthe onium salt of the 2-halogenated aza-arene employed in said Step Abeing selected from the group consisting of onium salts represented bythe above indicated formulas II and III wherein: R⁰ is a halogenselected from the group consisting of Cl, Br, F, and I.
 6. A method forsolubilizing a taxo-diterpenoid as described in claim 4, comprising thefollowing additional step: after said Step A Step B: converting theonium salt of the taxo-diterpenoid-C^(n),2-O-aza-arene derivativeproduced in said Step A to a taxo-diterpenoid:protein conjugate bydisplacement of 2-O-aza-arene and conjugation with a serum protein, thetaxo-diterpenoid:protein conjugate having high solubility.
 7. A methodfor converting an onium salt of a taxo-diterpenoid-C^(n),2-O-aza-arenederivative into a taxo-diterpenoid:protein conjugate, the methodemploying the following step: contacting the onium salt of thetaxo-diterpeniod-C^(n),2-O-aza-arene derivative with a serum protein fordisplacing 2-O-aza-arene and conjugating the taxo-diterpeniod with theserum protein to produce the taxo-diterpeniod:protein conjugate, the2-O-aza-arene being selected from the group consisting of onium salt Iand onium salt II represented by the following formulas:

wherein: Z¹ and Z² are each selected from the group consisting of C andN; Z³ is selected from the group consisting of S and O; R¹ is selectedfrom the group consisting of C₁-C₆ alkyl, allyl, arenxyl, propargyl, andfused aryl; R² and R⁶ are each selected from the group consisting of H,C₁-C₆ alkyl, allyl, arenxyl, progargyl, and fused aryl; if Z¹ is C, thenR³ is selected from the group consisting of H, C₁-C₆ alkyl, allyl,arenxyl, propargyl, C₁-C₆ O-alkyl, OH, halogen, and fused aryl; if Z¹ isN, then R³ is absent; R⁴ and R⁸ are each selected from the groupconsisting of H, C₁-C₆ alkyl, allyl, arenxyl, propargyl, C₁-C₆ O-alkyl,OH, halogen, and fused aryl; and if Z² is C, then R⁵ is selected fromthe group consisting of H, C₁-C₆ alkyl, allyl, arenxyl, propargyl, C₁-C₆O-alkyl, OH, halogen, and fused aryl; if Z² is N, then R⁵ is absent; andS⁻ is a counter ion.
 8. A method for converting an onium salt of ataxo-diterpenoid-C^(n),2-O-aza-arene derivative into ataxo-diterpeniod:protein conjugate, the method employing the followingstep: contacting the onium salt of thetaxo-diterpenoid-C^(n),2-O-aza-arene derivative with a serum protein fordisplacing 2-O-aza-arene and conjugating the taxo-diterpeniod with theserum protein to produce the taxo-diterpenoid:protein conjugate, whereinthe onium salt of the taxo-diterpenoid-C^(n),2-O-aza-arene derivativeproduced being represented by the following formula:

wherein: C^(n) is selected from the group consisting of C⁷ and C^(2′);R^(x) is selected from the group consisting of Ph and tBuO; R¹⁰ isselected from the group consisting of OAc and OH; R^(y) is a C-2substituent selected from the following structures:

R^(2′) and R⁷ are each selected from the group consisting of OH and anonium salt of a 2-O-aza-arene, with the proviso that at least one ofR^(2′) and R⁷ is said onium salt of the 2-O-aza-arene, said onium saltof the 2-O-aza-arene being selected from the group consisting of oniumsalt I and onium salt II represented by the following formulas:

wherein: R⁰ is oxygen and is bonded to C^(n); Z¹ and Z² are eachselected from the group consisting of C and N; Z³ is selected from thegroup consisting of S and O; R¹ is selected from the group consisting ofC₁-C₆ alkyl, allyl, arenxyl, progargyl, and fused aryl; R² and R⁶ areeach selected from the group consisting of H, C₁-C₆ alkyl, allyl,arenxyl, propargyl, and fused aryl; if Z¹ is C, then R³ is selected fromthe group consisting of H, C¹-C⁶ alkyl, allyl, arenxyl, progargyl, C₁-C₆O-alkyl, OH, halogen, and fused aryl; if Z¹ is N, then R³ is absent; R⁴and R⁸ are each selected from the group consisting of H, C₁-C₆ alkyl,allyl, arenxyl, propargyl, C₁-C₆ O-alkyl, OH, halogen, and fused aryl;and Z² is C, then R⁵ is selected from the group consisting of H, C₁-C₆alkyl, allyl, arenxyl, progargyl, C₁-C₆ O-alkyl, OH, halogen, and fusedaryl; if Z² is N, then R⁵ is absent; and S⁻ is a counter ion.